Astronomy Cast

Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Good! And where are you this week?

Pamela: I am in Austin, Texas at the 219th meeting of the American Astronomical Society.

Fraser: That’s good. So you are like buried in space news.

Pamela: I am not only buried in space news, but I’m among my people. It’s a good place to be.

Fraser: [laughing] Among your people, right! With your flock – that’s good!

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Fraser: Alright, so this going to be one of those “how we know what we know” kind of shows. How do scientists determine the ages of things? How do we know the age of everything from stone tools to the age of the Earth to the Solar System to the age of the very Universe? Alright, Pamela, so I think that was sort of the plan here, that we’re going to sort of explain to people how we know what are the various measuring sticks – age measuring sticks that astronomers use and scientists use to figure out how old everything is? And I thought, well, why don’t we start kind of close to home and think about, you know, when scientists discover some civilization, they discover stone tools, they find an archaeological dig — how old is everything that was in that dig? How do they know how old that is?

Pamela: It all pretty much boils down to radioisotope dating, and looking to see what’s in what sedimentary layer. One of the things that is a blessing and a curse — and I say curse because it leads to cancer now and then and that’s never a good thing — is a variety of the atoms that get created in supernovae and through other high-energy processes aren’t stable, and they’re not stable on varying time scales, so some things it might be — you set them on the table, and say you have a thousand atoms, well, you wait an hour and you have 500 atoms of what you started with, and 500 atoms is what’s called a daughter material, a daughter atom, and so you can actually look to see how much, what the ratio is between these two different atoms, and based on the ratio, you can see how many half-lives have gone by. Now, if you have something that decays quickly, that’s only good for time dating something in the recent past. I know as a small child, I was nerdy enough that I knew about carbon dating, and I was terrified that my teachers would use the carbon in my pencil to figure out I didn’t do my homework on time because I was that kind of a nerd and lacked the level of understanding I needed.

Fraser: …or you know overestimated the abilities of your teachers.

Pamela: Exactly. Exactly, but the thing is — carbon doesn’t decay on that type of a time scale, so we can only use carbon to date things in the distant past. We can use other forms of dating for the recent past, and through all the different atoms that we have that decay on the time scales of minutes to hours to days to weeks to years to centuries, millennia, to millions of years by combining all of these different types of radioisotope decay, we’re able to very carefully measure the age of different materials that contain these radioactive processes.

Fraser: And so do scientists have these overlapping methods of radioactive decay, and can they go from really, really short events all the way to the age of the Universe? I mean, are there any gaps in this?

Pamela: Well, so in general things that decay quickly are also things that we have to generate in cyclotron laboratories, so it’s not like there’s piles of polonium-120 lying around, so for the most part, the way we get to the things that we can radiocarbon date, and other things like that is we have to go through the archaeological record. So you look for those points where you’re able to bridge from our known understanding of the past of humanity to “A-ha! I found a radioisotope that has decayed in a useful manner,” and from there we just bridge our way backwards. And we do look for the times where we find in materials more than one of these radioisotopes, and just keep building our way backwards.

Fraser: And where does it sort of fall apart? I mean, does each isotope only give you so much, and then it’s just not useful anymore?

Pamela: Yeah, well, it’s a matter of…there’s just not going to have had been enough left at the end of the period. It’s the, well, you go half way to the wall, half way to the wall, half way to the wall, and never actually make it to the wall. At a certain point you have run out of atoms to decay, so you eventually get far enough back in time that the sample you’re looking at has completely decayed into its daughter atoms.

Fraser: Right. And I guess you can imagine, that’s kind of like you’re looking at ice melting. You’ve got a piece of ice on a plate and it’s in the living room, and you look at it and it’s unmelted, and you go “well, that ice was clearly just brought out seconds ago,” and then it’s kind of half-melted and you know it’s been within the last, you know, less than an hour, but more than a couple of minutes, but if it’s just water, it could have been there for a couple of decades.

Pamela: Exactly. Well, not decades, then it evaporates.

Fraser: [laughing] I know — it evaporated. I know, I know, I realized that as I said it. OK, great! So then, which is the tool that they would use? We’re going back to my first example, right? We’re going to take a look at stone tools left by Neanderthals –what is the method that they would use to date that kind of human civilization stuff?

Pamela: So this is where we often use carbon-14. It’s a naturally occurring radioactive form of carbon, and the nice thing about it is human beings tend to pick it up, plants pick it up, all of us…we’re made of carbon, and so we become partly radioactive in the form of carbon-14, and so you can look at the leftover logs in fire pits, you can look at the leftover carbon in the bones and you can start to get at how old things are. carbon-14 has a radioactive half-life of 5730 years, so you can basically step back in these intervals of 1000s of years, tens of 1000s of years…in fact, we think the limit for using this is actually somewhere around 60,000 years in the past that this starts to become a not-entirely-useful way of studying the age of things in our environment.

Fraser: Right. OK, so then you’ve got the quantity of the carbon-14, and then it’s going to… you’re going to be able to measure that ratio of what you had carbon-14 and the various daughter elements that it’s going to decay into, and get a sense of how old it is. OK, so we’ve done, then, carbon-14, and you say that, sort of, how early can we measure with that? Within a few hundred years, right? And then…

Pamela: Well, a few hundred years starts pushing it because you haven’t had that much…I mean, its half life is 5730 years, so a quarter of it will have decayed in 2600 years, and so you want to get closer to the 1000 year mark than the couple-hundred year mark.

Fraser: Right, so definitely 5000 years is great, but you don’t want to be measuring beyond 60,000 years.

Pamela: Yeah, that’s a comfortable place to be.

Fraser: Alright, so the next age of something, I would assume, is going to be like rock formation, lava flows, things here on Earth that we’re going to try and date.

Pamela: So we also look at things like the uranium to thorium dating method, which looks at uranium-234 decaying into thorium- 230 and this is something where we’re looking at processes that, depending on where we are in this, there’s a whole network of things in this that decay. We’re looking for that combination at a half-life of 80,000 years, but we can also look at uranium-235 which decays into the generally-not-talked-about-in-chemistry-class protactinium-231, which has a half-life of 34,000 years, so by looking at these different decay paths and looking at their different daughter processes, this is where we can start getting into more of the geologic record, getting back into the hundreds of thousands of years over the course of their decays.

Fraser: And, same thing if they’re going to measure… I’m trying to think, soil, sediments, or ice cores — things where you’re looking at hundreds of thousands to millions of years old. So you’re telling me there’s little bits of uranium kind of everywhere for the measuring?

Pamela: It’s actually a really good thing because it’s part of what keeps our planet warm. Our planet is a lot warmer than it would be strictly from sunlight hitting it, and an atmosphere that blankets it and keeps some of the IR radiation trapped in. Our planet’s internal temperature is driven by the constant decay of radioactive particles. It provides heat, and that’s a good thing because heat helps to provide life, so be glad for the radioactive materials.

Fraser: Right. So then how, I mean, you keep pushing that further and further back, but I can imagine if the whole surface of the Earth is being re-surfaced (thanks to plate tectonics and such like), that there’d be no way to figure out how old the Earth itself is, and yet we know quite precisely how old the Earth is. So, how did…how on Earth did astronomers figure that one out? Geologists…we’ll let the geologists have that discovery.

Pamela: We do actually look for progressively older and older rocks, and we do find rocks that are billions of years old, and this is where we start pressing ourselves backwards with things like looking at samarium and neodymium, and their decay rates, which get us back to millions of years to now a billion years, so we do have some pretty old rocks, but you’re right — we are pushing the billions of years limit. So we look at sedimentary histories; we look at the way things are capable of moving, and then we start looking at cratering histories on other worlds, and we start grabbing asteroids. Asteroids are really, at the end of the day, the final authority on the original chemistry and the age of our solar system, so we wait for asteroids to actually come to us (we call them meteorites by the time they reach the surface of the planet), and take them to labs, and this is part of why scientists are so avidly collecting meteors, and, well, we know that lots of amateur astronomers are enthusiasts. There’s lots of scientists who would like to take a core sample of that big rock you have found and put on your shelf as a trophy object. That’s actually a piece of data that hasn’t been collected that you’re keeping on your shelf.

Fraser: And so…and so the theory goes that if you’re going to find a meteorite and determine how old that meteorite is, you’re going to know how old the Earth is? I don’t understand.

Pamela: Right. So the idea is the entire Solar System formed at once, and so the age of the Earth is the age of, well, not the Moon — it formed later; it’s a blasted-off piece. So it’s sort of like its materials formed at the same time, but it was part of two other things, but all of the materials came together, maybe not in the same structure they’re in now – big asteroids have broken apart into smaller asteroids, things have hit each other, creating the Earth’s moon, but all of this stuff in our Solar System formed out of the same solar nebula, formed at the same time, and so if you can age a meteorite, you’ve aged the entire Solar System. Now, the more of these that you age at once, it’s like taking more and more measurements. You’re able to get a more and more precise understanding of the age, so this is where we’re constantly trying to catch and collect and understand asteroids.

Fraser: And was this always assumed to be the case, or were astronomers not even really sure that all of the meteorites are the same age?

Pamela: Well, it was one of those things where you postulate it and hope it’s true. And as we’ve measured it, it’s come out to be we’re able to put very good limits on the age of the Solar System using meteorites.

Fraser: Now, you hinted at for a second there that astronomers use cratering on places like the Moon, and I know on Mars and stuff… they’ll use that as a totally different method for determining the age of things.

Pamela: Well, so there’s two different ages that we worry about: one is when did this stuff form, and then the other is when did the surface of the stuff form. So when you look at the Earth, our surface is extremely young; in fact, there are volcanoes if you look at bits of the surface – like Etna’s going…I think earlier this week it went off, and that surface is measured in days in terms of its age. Well, when we look at the Moon and we look at Mars and we look at other rocky surfaces, the only way we have since we can’t readily go there all the time of getting the age of the entirety of the surface is to look at cratering histories. And this is where we actually try and get the public’s help because we want to measure the ages of as much of the surface as possible so we can start understanding what was the collision history in the past, what was the bombardment history in the past, and we create projects that ask you to help us train computers to more effectively measure craters for us because — let’s face it, at the end of the day, measuring craters is fun for a while, and then you want to do other things, but we also ask you to measure craters for us.

Fraser: Right. This is a project that you’re actually working on, right?

Pamela: This is…and you’ve been giving us server advice, so we’re launching a new project called Moon Mappers with CosmoQuest, which Fraser and I have talked about a bit in some of our other hang-outs. CosmoQuest is a community where we’re hoping that you’ll come and learn like you do with AstronomyCast, and listen to Fraser and I, and then apply all these things that you’re learning to actually doing science. And Moon Mappers is our very first science project. It’s part of the Lunar Reconnaissance Orbiter mission (not the orbiter itself), and we’re asking you to help us correct crater finding algorithms, to go in and tell us where does the software screw up, and fix their outputs, and to help us measure the age of various surface features on the Moon.

Fraser: So, this episode of AstronomyCast is brought to you by CosmoQuest. We’re sponsoring ourselves.

Pamela: Something like that. Yeah.

Fraser: Right? But no, I mean, our goal has always been to get everybody involved in space and astronomy to some degree, and we’re trying to…you know, Pamela’s been working with NASA and other science agencies to get data from the spacecraft, and then bring in the general public to help in actually creating science that then gets used for real scientific research that may not even be possible to be done, and so this is one of those projects, and now we’ve got this umbrella organization where we can…and sort of server and hardware and software where we can actually do more and more of this. So hopefully you’ll hear a bunch more of these kinds of announcements and more of these projects as we go on, and we’ll recruit as many as we can to do some real science.

Pamela: And as we move forward doing this, we’re going to be working to determine the ages of different features on the asteroid, Vesta — we’re working with the Dawn mission. On the surface of Mercury we’re working with the Messenger mission, and in all these cases we’re looking for those places that have extremely few craters – those are the young surfaces; we’re looking for those places where you have crater bombarding on top of crater, crater inside of crater, these places that are extremely rich in craters –those are the old places, and then we’re looking to see, “OK, can we trace this area that’s almost devoid of craters, and thus actually trace out where there was a ton of lava from an ancient volcano or a more modern volcano?” We’re trying to understand what was the geologic history? How recently were there volcanoes active on the Moon? That’s something I always am startled by is there was actually volcanism on the Moon. Imagine what that must have looked like to the amoebas swimming around on the planet not paying any attention. It was an amazing past, and we can better understand that past by all working together.

Fraser: But how accurate is this method of determining the cratering? I mean, I’ve heard astronomers say, “Well, you can see that region of the Mars is a billion years old,” or “This part is very active and is about a million years old,” but how can we know that this amount of craters is a billion, and that amount of craters is a million?

Pamela: Yeah. It gets tricky, especially since the cratering rate isn’t constant with time. And we don’t know how it varied with time, and so right now what we do is we bridge together the different periods using actually Moon rocks. So the astronauts when they went to the Moon, and the spacecraft (mostly Russian) when they went to the Moon and brought back rocks, they brought back rocks from a variety of different terrains. They brought it back from nice, young areas; they brought them back from older areas, and with each of these rocks using the radioisotope method, we were able to determine, “This area with this cratering rate is this age; this other area with this other cratering rate is this other age.” Now, the problem that we run into is we’ve only done these sample return missions for the Moon. We want to do them for Mars. This is part of the plan for Mars MAX-C mission that’s planned for the next decade. We want to do this with asteroids, and right now we’re sort of making assumptions. We’re saying, “OK, so we think some things happened earlier on Mars — it’s further out. Some things happened later for Mercury — it’s further in.” So we’re making rough corrections to what we know based on the Moon, based on theoretical models, but for the most part we’re within a few hundred million years, which isn’t entirely a comfortable place to be, but that’s the best we can do until we bring back enough rocks to say, “OK, this type of terrain is this. Period. We’re done for the entire Solar System.”

Fraser: Right. I can see that part of the process is that the astronomers have…they’ve got pretty accurate measurements on the Moon, and they’ve been able to sort of correlate the cratering with the Moon rocks that they’re bringing back, but then they’re taking that cratering estimate and using that as a measuring stick for other parts of the Solar System, but they haven’t backed it up yet with actual samples, which is, you know, hopefully going to come within the next few decades. OK, alright, so that’s enough sort of stuff in our Solar System. Well, I guess there’s one more object in our Solar System we should probably take a look, and that’s the age of the Sun, but obviously we can grab parts of the Sun.

Pamela: No. [laughing] That would be dangerous.

Fraser: …and we’re making a pretty big assumption that the Sun formed at the same time as the planets in the Solar System. So how do astronomers know this?

Pamela: Well, so at a certain point, we do assume the Sun formed at the exact same time as everything else in the Solar System, but moving beyond that, we also look at stellar evolutionary theory models, where we say, “OK, the Sun is this size, it had to go through this in the past, it took it this long to get to the stage it’s at now.” So that’s one way of doing it, and then, where we can, we also use, well, in this case instead of radioisotope dating, we call it cosmo-chromatography, and this is where we actually use the exact same idea, but with different types of elements. For instance, strontium is one that gets used when we look at…or scandium are elements that get used when we start looking at stars and figuring out, “well, how old is that?” So there’s a whole variety of isotopic combinations that can get us gigayears of age.

Fraser: Right, but we can’t take, again, a piece of those distant stars, stick them in our gas chromatograph and get the age. Like, what is the method that they use to determine even just the chemical elements in the stars? How do they do that?

Pamela: So the nice thing is the Sun is actually in some ways a gas chromatograph for us. One way you can determine the composition of things here on Earth is you burn them, and you look and see what emission lines are present in the heated up materials, and you create spectra and use the spectra to get at the composition. Well, the Sun you don’t exactly need to set on fire — it’s kind of already there, so when we look at the Sun, all of the atoms in our outer atmosphere, depending on the exact energies, are either emitting wavelengths of light that we can see as spectra emission lights, or much more commonly, they’re sitting there absorbing out radiation and creating atomic absorption lines, and by measuring the depth of these absorption lines (do they absorb all the radiation in a given wavelength of light? Do they absorb just a little bit of light in a given wavelength?), by looking at the depth of the lines, it tells us how much light has been absorbed and a variety of other things, like what are the ratios at different temperatures? We can get at the temperature of the star, and then we can get at the surface gravity of the star, and then we can get at the abundance of materials within the star. Unfortunately, it’s a three- variable problem, and you have to solve for all three variables, which can get really annoying, but when you’re done you know exactly what a star is made of.

Fraser: And so by, again, measuring the ratios of those various elements, which are known to decay at very specific rates, you can determine how old that star is.

Pamela: Exactly, so here we again still use uranium, in this case, we’re looking at uranium-238, which has a half-life of 4.47 billion years, and it decays into lead-206. We’re also looking at rubidium, which has a 48-gigayear life. We’re looking at aluminum, which has a .75-megayear half-life. So we have all these different atoms that we look at, and by looking at all these different combinations, we’re able to fine tune to get a good sense of how old things are. Now the only problem with this is you have to be able to get extremely high-resolution spectra to see all these different lines, and to get high-resolution spectra you are somewhat confined to only looking at the brightest stars, and to a certain degree, only using the biggest telescopes, so it limits how far away you’re able to use this method.

Fraser: OK, fine. How do astronomers know how old the Universe itself is? You know? Cause, I mean, you can’t go and grab pieces of Universe stuff at the Big Bang, you know, and measure its age, so that’s gotta be the final, ultimate challenge. How on Earth, do…how on Earth, how on Earth do astronomers determine just how old the Universe itself is?

Pamela: Well, for the Universe in general, because that’s such a controversial number in so many ways, we need to have multiple lines of evidence. So the first thing, we say no star is allowed to be older than the Universe — that would just be silly.

Fraser: That’s fair.

Pamela: Yeah, so we just look at the oldest stars and use stellar evolutionary theory models, and we’re able to figure out from the cooling of white dwarves, from how long it takes stars of different masses to become red giants, that globular clusters, which are the oldest collections of stars in the Universe are 12 billion years old, give or take. So we know the Universe is more than 12 billion years from looking at the stars, and then beyond that, we have to start looking at cosmological models and matching the predictions of those models to what we see when we examine the cosmic microwave background, and the evolution of structure in the Universe, and from the using the WMAP (the Wilkinson Microwave Anisotropy Probe), we’re able to study what was the distribution of hot spots and what was their size on the cosmic microwave background radiation, and we’ve done entire shows on this so you should go back and listen to those.

Fraser: …one whole episode on just how old the Universe is.

Pamela: Yeah, so go back and listen to that, but it boils down to a whole lot of scary, complicated math (and geometry, more to the point), that tells us that our Universe is more than 13 billion years old. So the stars and all of the fancy calculations using the cosmic microwave background all get us to the same place — and it’s all consistent with what we see from radioisotope dating.

Fraser: And now we have that really precise, precise number. I mean, now we know it’s 13.75 (plus or minus .17) billion years old.

Pamela: Yes, and they just keep adding new decimal points; the accuracy just keeps getting better.

Fraser: As successive versions of these surveys of the microwave background radiation come out with more sensitive instruments, they’ll just keep adding decimal places, but we’re pretty confident with the 13.7 part.

Pamela: Yeah.

Fraser: That’s really cool.

Pamela: So we live in an old universe on a fairly young planet, and we’re still at the beginning of the Universe, but we’re at the most interesting time. And so all these techniques have ganged up to give us a consistent result, and we’ll continue to work into the future, and it’s just one of those neat things to see the pieces building together.

Fraser: Sounds great! Alright. Well, thanks a lot, Pamela.

Pamela: My pleasure.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 246: What if Something Were Different?

admin — Sun, 22 Jan 2012 05:53:27 +0000

The number of moons, the age of the Sun, and our placement in the Milky Way all had an impact on the formation of the Earth and the evolution of life on our planet. But what if things were different? What would be the implications?

Show Notes

Sponsor: 8th Light
Google+: Pamela and Fraser
Watch the video of this episode
Martha Haynes and the Extragalactic Research Group
Early star formation history
Paper: Tracing Cosmic Star Formation History to its Beginnings
Gas Giants Expelled from the Solar System
End of Everything — Universe Today
If We had No Moon — Astrobiology Magazine
What if Earth had several Moons? — Cornell University
What Would Earth Be like With Two Suns – Life’s Little Mysteries
Three Body Problem

Transcript: What if Something Were Different?

Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain, I’m the publisher of Universe Today and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Doing really well. So once again we’re recording this episode of AstronomyCast as a live Google plus hang-out on air, which means that if you’re a big fan of AstronomyCast you can actually watch us live as we record the show and go through all kinds of audio hassles and headaches, and…yeah. But it’s pretty cool, and so we’re still figuring out all the bugs and if you want to check it out you can join us live. The easiest way to do that is to circle me or Pamela on Google plus, and then you’ll see announcements of when we’re about to record. And as we sort of settle out the technology, we’re going to do this more often and do it on a more regular schedule. In fact, the easiest way to find us or me anyway is…I’ve actually redirected FraserCain.com to my google plus page.

Pamela: Wow!

Fraser: Yeah, I know, that’s brave, right?

Pamela: Yeah!

Fraser: So…cool! Alright, any more announcements? No, we’re good — let’s just rock.

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Fraser: So the number of moons, the age of the Sun, and our placement in the Milky Way all had an impact on the formation of the Earth and the evolution of life on our planet, but what if things were different? What would be the implications? So the goal of this show, and this was suggested by a listener, was what would life be like, or the Earth be like if some aspect, some physical aspect of the Universe, was different? If we had a different number of moons around the Earth, if we had a different structure of the galaxy, if we were located in a different place, if we didn’t have some of the giant planets, different metalicity of the star, and just what would the implications? What do astronomers think would be the outcome? So, Pamela, let’s start with sort of the big picture and then we’ll sort of zoom in as we go.

Pamela: OK.

Fraser: So, you know, we know that our Milky Way is located in a galaxy cluster. We’re in the Virgo Supercluster in the Local Group…

Pamela: We’re in the Local Group on the verges of the supercluster, we’re not really in the supercluster, but we will be — but we’re not there yet.

Fraser: But when you look out into the Universe with the Hubble space telescope and things like that we see regions with tons of galaxies clustered tightly together, and other regions where the galaxies are more far-flung apart than what we have here. Some have…so I guess just galaxy density, let’s say that we ended up in one of those situations? How would things be different?

Pamela: Well, we probably wouldn’t have ongoing star formation. One of the things that I actually studied as part of my doctoral dissertation is how the lives of galaxies change as they go from low-density environments to high-density environments over the course of the history of the Universe. And what we find is in the biggest clusters out there, the Bell clusters that look so beautiful with all their gravitational lensing in Hubble pictures – these clusters don’t have any star formation. What’s happened is over time, as the galaxies have swept one past the other, the gravity of them tearing at each other has sucked all the dust out into the spaces between the galaxies, and without dust there’s no star formation. So in a large cluster, much larger than the one we live in, with all these interactions over the billions of years of our Universe, you crush star formation, so we’d be living in a dead system — no Orion nebula to look at, no Pleiades to look at, the Hydes might not even have had a chance to form. It’s much more depressing.

Fraser: Right, and so it would less the chance…the stars would have been sort of young and hot, and then all have burned out, or be burning out right now and you just wouldn’t have the same…but on the flipside, what if you had the galaxies too far flung apart?

Pamela: Well, in that case, it would simply be a boring sky. There’s all these isolated galaxies and the places that we look trying to find nothings. There’s a researcher, Martha P. Haynes, who’s looked in these giant voids trying to find someplace empty, and what she finds is isolated spiral galaxies. If you let a galaxy form, leave the sucker alone, most of the time it’s going to end up being this nice, beautiful spiral galaxy, lots of star formation – not too different from the place we live.

Fraser: But is there a situation…it’s the galaxy collisions that help some aspect, causing more star formation and helping with the amount of metals in the stars, things like that. I mean, do you need a certain amount of galaxy collision, or is none OK?

Pamela: No. Well, once you build the galaxy, I mean, we think that large galaxies like our own form out of little tiny puffs of galaxy that build up over time to form the giant galaxies, but once you get to the giant galaxy stage, any galaxy interactions that you have are either going to be minor things — like we keep eating dwarf galaxies, it’s what the Milky Way does — or they’re going to be giant star formation, crushing events that initially trigger massive star formation. I mean, that’s the irony in this: you get two galaxies that interact just right, you get this massive burst of star formation, but then after that, nothing — no more stars, and without new star formation, there’s no pretty nebula to look at, but worse than that, there’s no new planetary systems forming. If you have this happen too early in a galaxy’s life — that means that high-metalicity stars haven’t had a chance to form; you might not end up with nice, interesting planetary systems. This massive burst of star formation’s going to create everything, but there’ll be nothing coming after that.

Fraser: So then let’s roll back the age of the Universe a bit. So what if events conspired, and the Sun formed much earlier or our galaxy’s evolution, was much earlier in…after the Big Bang, like say almost right away? Like, I’m not sure how old the star could be, or how young a star could be after the formation of the Universe. What if we were as close as possible to, you know, the formation of the Universe early on?

Pamela: Well, if our Sun had been one of that 0th generation of stars which formed pretty much 400,000 years after the Big Bang, it would have been giant. It would have been a runaway star because it wouldn’t have had any metals to help it cool off. That’s one of those strange things in star formation.

Fraser: Right, so that’s one of those “we wouldn’t be here” situations.

Pamela: Right, and well, and there wouldn’t have been any of the stuff to make planets. Initially, it was hydrogen, helium, trace amounts of lithium, and beryllium — none of the silicon we need to make rock, none of the iron we need in our blood, none of the metals at all existed initially, so that first generation of stars, if we’d been one of the first generation of stars, no planets would have formed, and the Sun would have been this giant short-lived thing. So that’s just different.

Fraser: Then, you know, on the flipside, if we were trillions of years into the future, you know, where the expansion of the Universe is quite large…I mean, I know it would have implications for astronomy in that we wouldn’t see other galaxies. We might not even know that there was an expansion of the Universe at all, but would it have any impact? You know, will stars still be forming a trillion years down the road?

Pamela: No.

Fraser: No?

Pamela: No.

Fraser: Really? Wow.

Pamela: Yeah, that’s the thing to think about is our Universe is slowly using up all of the material or spreading it out to the point that it’s spread out so much that it can’t condense down into new stars. There’s a few exceptions; there’s repositories of gas that’s fairly high-density in the centers of galaxy clusters. That’s not going to change, but really hot gas doesn’t collapse into stars either, so we’re going to reach this point where all of the gas that’s cold enough to form stars is spread out so much it can’t collapse. All the gas that is dense enough to form stars is too hot to collapse down to form stars, so there’s this future of no more star formation.

Fraser: So we really are at the right place. So I guess we could have a more loosely organized galaxy cluster, but we really are at the right time for this one.

Pamela: Exactly.

Fraser: OK. So let’s focus in on the Milky Way then. Right now we’re located more closely to the outer edge of the Milky Way, nice and far away from the turbulent and crazy galactic core, but what if we were located much closer to the core?

Pamela: Well, we would have still formed, we could have still formed with planets, but the probability that we wouldn’t have had the outer parts of our solar system constantly harassed by stars passing nearby… yeah, that probability says that we would have been harassed by other stars, and one of the things that astronomers think is that some of the past epochs of heavy bombardment where, all of a sudden, all the random rocks, ice, stuff from the outer Solar System came plunging in, creating craters in the inner Solar System, there’s thoughts that some of that might have been triggered by a nearby star passing. Now, if we’re living in an extremely dense environment, the probability that there’s going to be these chance encounters with a star disrupting the Oort Cloud, disrupting perhaps even the Kuiper Belt starts to go up. There’s even the possibility that we’ll pass so close that…we don’t worry about collisions. The probability of a collision’s very low, but passing close enough that Jupiter gets stolen, that’s…[laughing] that could happen, and three-body encounters start flinging things in all directions.

Fraser: Right, so we’ve got this situation where a lot of the stars passing beside each other are just wrecking the structure of the Solar System, and so, you know, do astronomers think that if we…you know, once we can better map the star systems that are closer in to the core, they’re going to have sort of stolen planets? The planets being flung around, and…?

Pamela: Well, you can’t actually tell in a lot of cases if a star has stolen its planets, but what we do think is that there’s probably a habitable zone not just around stars, but around galaxies as well, and it’s that region within the galaxy where the probability of two star systems encountering one another is sufficiently low that you don’t have to worry about life getting disrupted by an overly close hot neighbor coming through.

Fraser: Right, so you’ve got enough time of not getting your solar system wrecked that life can form and things can be stable. So then what about on the flipside, right? What if you’re further out in the galaxy? What if we ended up forming, you know, right at the very rim of the galaxy?

Pamela: [missing audio]

Fraser: But it wouldn’t really have any implication, but what about amounts of metals, or radiation?

Pamela: So the thing you do have to worry about is if you’re still in the disk of the galaxy, most of the disk of the galaxy still has metals in it, but as you start to get out into the halo of the galaxy – this is the spheroid of globular clusters and random stars that just sort of… it’s still part of our galaxy, but isn’t part of the pretty disk we think of. Those stars are generally so metal-poor that they can’t form planets, so once you get to these older areas…and that’s the thing too is these are stars that formed much further back in the history. In fact, for a long time, globular clusters were thought to have been some of the very first objects that formed in the Universe. These systems – they don’t have the metals you need to have planetary systems, and so far we haven’t found any planets in globular clusters.

Fraser: Now, you mentioned globular clusters. That would be crazy, I mean, we formed in a nebula kind of like the Orion nebula or the Pleiades or the Hides…but what if we formed in a globular cluster? Cause then the stars would be still around us, right?

Pamela: Right and there’s some fabulous art, I believe, by the artist Loretta Cook, who sat down and then figured out all of the science behind what it would look like, and literally… if you have a thin atmosphere, so you don’t have to worry about scattering of light that creates an opaque, blue atmosphere like what we have, if you’re sitting on an atmosphere-free moon, for instance, as you look about, it’s stars everywhere, and it’s not just stars little points, it’s you can resolve the disks, you can go, “Oh wow! There’s a massive solar flare on that thing that’s half a light year away. There’s…” You can start to see details.

Fraser: Like Venus brightness? Like moon brightness?

Pamela: Somewhere between the two…

Fraser: Yeah, OK, alright, so brighter than Venus…wow! And depending on the age of the cluster, you’d have variation on the brightness of stars. If the cluster was older, you’d have just a smaller…

Pamela: Well it would be red in general, so imaging Betelgeuse everywhere you look.

Fraser: Right, but you know, we typically don’t see those. We see the red giants, but we typically don’t see the red dwarves as easily just because they’re dimmer, and so we don’t see them very far away, but if they were packed in a globular cluster, they’d be all over the place. OK, so then let’s talk about the Solar System itself. So what if, for example, I mean, we have this sort of nice, series of planets, and then we have some gas giants, and then we have this, you know, the icy area around that, so what if, you know, some of those things were different? For example, what if we didn’t have some of the gas giants?

Pamela: Well, the gas giants are actually kind of useful because they’re vacuum cleaners gravitationally. We used to think that things hitting Jupiter was probably a once-in-500-year kind of event, but we’re [laughing] now learning, yeah, we’re now learning if you look at Jupiter long enough any given year, you’re going to see it get hit by something.

Fraser: Like, we’ve had two major impacts in the last 20 years.

Pamela: I think…aren’t we up to three now?

Fraser: Yeah, but anyway two big ones for sure: Shoemaker-Levy 9, and there was another one just a few years ago that smashed into Jupiter. So yeah, this is happening a lot.

Pamela: So you have Jupiter eating things, you look at all the outer planets have what were probably once upon a time Kuiper Belt objects or comet cores now as their moons… Gas giants are vacuum cleaners; they protect us from some of the large rocks that might otherwise come into the inner Solar System, and by protecting us by eating things, that means there’s a lower probability that we’re going to get hit by things, so it’s thought that perhaps you need these giants out there vacuuming up as many rocks as they can to lower the probabilities low enough that life has a chance to evolve.

Fraser: But in our solar system, Jupiter is sort of the size that it is… and you know, Saturn and Uranus and Neptune, but at this point now with the thousands of planetary systems that have been discovered, thanks to Kepler, you know, we’re seeing every variation. So there would be worlds with far more gravity, a lot more mass — I know they don’t get a lot bigger than Jupiter, but they would have a lot more mass than Jupiter. So you know, if we had some of those, would that have an implication?

Pamela: Well, so here you have to worry where’s the trade off? When our planet first formed, it got completely blasted dry by an early hot Sun, and so that dry Earth got the oceans we now enjoy from comets hitting the early planet, and re-giving us back our volatiles. Now, if you had too heavy an object, or too many heavy objects protecting us, then maybe we wouldn’t have gotten enough water, but that’s really one for the planetary modelers to play with, but there is this trade off where you don’t want to get hit too much, but you do need to get hit some to get your volatiles back.

Fraser: For the right period of time for…to give life a chance to form, and then what about the rocky planets, then? We have the four rocky planets that we have. Would it have an impact if we had more or less?

Pamela: Boring skies? I mean, that’s the impact of things that wouldn’t cause “negativeness” is they just make the Universe more boring.

Fraser: Right, but if we end up with say a Mars-sized object in the same orbit as the Earth, as we’ve seen, you know, that has it’s implications.

Pamela: Yeah, right.

Fraser: That’s the Moon, right?

Pamela: Yeah. [laughing] Once the Universe, once the Solar System is stable, what the rocky planets look like don’t matter. Having extras that hit you – that matters.

Fraser: Right, right. So it’s really all about…again, it’s sort of back to that clearing out the Solar System.

Pamela: Yeah.

Fraser: OK, well, now let’s take a look at our Sun. So we talked a bit about sort of if our sun formed at different periods of the Universe, if it formed early on in the Universe or later, but what about the age of the Sun? The Sun right now is 4.6 billion years. What if for some, you know, I mean…but we’ve had life on Earth for almost the entire period, so what if the Sun was younger right now?

Pamela: Well, the younger Sun was hotter and our planet actually had a point when its temperatures were hotter due to that hotter Sun, but at the same time, the composition of our atmosphere was different early on, so it’s hard to figure out how to put all of these different variables together. We had hotter sun, we had different atmosphere, and we had a planet that was quite honestly not acceptable to us because it was so methane-rich. It wasn’t until the Sun got a little bit older and a little bit cooler that we had an oxygen-based atmosphere to enjoy.

Fraser: So, I mean, that took billions of years to get going, right?

Pamela: A couple of them…not a lot. It’s really amazing how quickly our planet settled down to start getting amoebae, or amoebas.

Fraser: Right, but again, let’s run the clock forward. What if we were 5, 6, 7 billion years – the Sun was older?

Pamela: So when the Sun gets older, we’re kind of in trouble here on the planet Earth. Our Sun is going to switch how it produces energy in its core, and when it does this it’s going to bloat itself out and undergo extreme amounts of mass loss, and the combination of getting larger, getting brighter – it’s going to get cooler as well, but you still move that surface right against the surface of the planet and it doesn’t matter if it’s a little bit cooler. We’re going to get blasted, and essentially imagine broiling the surface of the planet and blasting it with a wind that is high-energy enough to remove the Earth’s atmosphere, and you’re looking at our future.

Fraser: Right, and we’ve talked about this in earlier podcasts that the Sun is actually heating up right now. You know, not “global warming” heating up, but heating up over the next 500 million to a billion years. It’s going to make temperatures on Earth a lot hotter than they are today, and this is just the process of the Sun converting hydrogen to helium and sort of changing its energy up, so actually that number is pretty tight. I mean, we’re within a few million years from [missing audio] life forms to be able to live?

Pamela: Yeah, the big thing that we have to worry about is as the Earth’s temperature goes up, it’s going to cause the oceans to evaporate, which is going to put more water vapor in the atmosphere, which is going to cause the planet to heat up, which is eventually going to cause a runaway greenhouse effect, which will evaporate our oceans completely. No surface water — it’s a lot harder to live.

Fraser: Right, and then I think one of the ones that’s most interesting to people is the Moon, right? I mean we have one moon, and we’ve mentioned this a lot that the Moon is kind of important. Why is the Moon important?

Pamela: [laughing] Well, gravitationally it stabilizes our planet. If you’ve ever watched a top when you set it spinning, this little top happily precesses around and around and around, and the amount that a planet does the same thing varies from world to world, and here on Earth, our precession is at least somewhat stabilized by having the Moon there, so for us, the Moon is a way of keeping that spinning top somewhat upright. Now, the other thing that the Moon does is, just like Jupiter, it helps sweep things up. Things hit it; we look at it and we see the poor thing has been completely obliterated with craters. Every part of its surface has been hit by something at some point in the past. This is what creates the regolith that we see. Now, the Moon also has the effects of churning up the tides, so when you see the ocean moving, that’s because we have a moon. And it’s thought without those tides, life might not have been able to evolve the way it did. Now, there’s still argument over whether life started in water, it started in volcanic springs, it started in dirt…we’re not sure where life started. It could have started in all of the above – that’s fine too, but no matter how it happened, we know that biological functions are at least in some part tied to the lunar cycle, so there’s a good chance that life would not be the way it is without our moon there.

Fraser: So then what if we had more moons?

Pamela: That would depend on their spacing, their sizes…more moons, if you have the Moon we have now, and then you’ve got a little one close in…

Fraser: Oh, OK. Sure.

Pamela: So imagine a little one close in, we call that one the International Space Station…

Fraser: Right, but if we didn’t keep boosting it up, it would crash.

Pamela: That’s true.

Fraser: So a little further than that…

Pamela: So you do have to worry about…and this is actually a problem Mars has in its future; it’s going to get bombarded with one of its moons in the future, so we’d want to have moons far enough out that they’re tidal effects cause them to keep going further out, rather than to come closer in, which would just be a bad thing, but as long as they’re small enough to not wreak gravitational havoc on our planet, then they simply serve as a protector that helps eat things headed our way.

Fraser: But you would get weird tides, right?

Pamela: It depends on the size. I mean, you can imagine if we had a much smaller moon in addition to the one we have now, it would be sufficiently small that the tides that it rose up (assuming it’s further away) would be so minor that they’d be washed out in the noise of the tides that are there. It’s sort of like if you’re at a rock concert, your phone ringing — you might notice, but barely.

Fraser: Right. I know that we get things lining up. We get the Moon and the Sun lining up — you get much bigger tides.

Pamela: Right, and you would see things like that, but it doesn’t mean that it would affect life.

Fraser: Oh! What if we had two stars?! What if we were in a binary system? I forgot to ask that. I wanted to ask that.

Pamela: We’ve actually seen solar systems like this. There’s lots of them out there.

Fraser: Yeah, this was thought to be impossible, right? And now, well, not so impossible.

Pamela: We have this one extremely endearing, old professor who keeps wandering through, and he’s like, “what about planets with more than one sun?’ And we’re like, “they exist!” and he’s like, “no!” He’s very cute and very, very old. So anyway, 61 Cygni B, it’s one of them. We see things like this: there’s the star Tau Boötis A, that has planets, and its companion Tau Boötis B (don’t say that one too fast with elementary school audiences) — all of these systems generally have widely-separated stars, and the beauty of these widely-separated stars is you end up with all the planets gathered around one of the stars, and the other one sort of hangs out, shining beautifully in the distance.

Fraser: So, it all depends on the distance?

Pamela: Yeah.

Fraser: If they’re too close, things won’t work out. If it’s really far away, things work out a lot better.

Pamela: If they’re close, then the planets start to experience what’s called a three-body problem, and those fling things, again, so any time you’re getting gravitationally interacting with three different objects, flinging occurs. So you need two things close together that you can treat as one thing, and then something else further away.

Fraser: I think that’s the whole theme of this whole episode, when you think about it, is it’s really about 3-body interactions.

Pamela: That’s entirely true.

Fraser: You know, that is, if it’s too much gas, too many galaxies, too many moons, too many planets, too many stars, then you get these 3-body interactions that wreak havoc. One last thing that I wanted to bring up is the mass of the Earth, right? I mean, the mass of the Earth that we have is…

Pamela: …kind of awesome.

Fraser: Kind of awesome, well sure! Yeah, but I mean, would things be different if the earth had double the mass? …half the mass?

Pamela: So if you adjust the amount of mass we have, assuming that the density doesn’t change, as we adjust the mass that we have, you run into things like well, if we get small, we don’t have enough mass to hold on to atmosphere.

Fraser: Like Mars…

Pamela: …like Mars. Now, if we get big, we kind of end up with too much atmosphere, so if you can imagine having a much thicker atmosphere, life’s still possible, but you’re going to develop entirely differently, and as you increase the pressure more and more, you can imagine needing exoskeletons to protect yourself. It starts to be much more like the situation life has at the bottom of the ocean, where life always finds a way given that it has the proper stuff, but it takes on a very different shape.

Fraser: Right, so I think in that situation I’d almost prefer to have more gravity.

Pamela: Yes, more gravity is good; less gravity is less atmosphere, which is bad.

Fraser: Which is bad…cool! Alright, and while this episode is running out, I was looking through some questions from people, so that’s kind of cool. Cool! Well, thanks a lot, Pamela! And thanks to everybody who watched this live episode of AstronomyCast. Your thoughts and ideas were very helpful — I stole them all.

Pamela: Thank you for joining us, and stay tuned – more of these are to come.

Fraser: And more good stuff…yeah. Absolutely. Alright, well, thanks a lot Pamela and we’ll talk to you next week.

Pamela: My pleasure. Thanks, Fraser.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 245: Calendars

admin — Tue, 10 Jan 2012 23:37:58 +0000

Our lives are ruled by calendars. And calendars are ruled by astronomy. As we near the end of 2011, and get ready to ring in the new year, let’s discover the astronomy underlying the days, weeks, months and years that segment our lives.

Ep. 245: Calendars
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Show Notes

Explantatory Supplement to the Astronomical Almanac
For all types of calendars, see The Calendar Zone
Calendars Through the Ages website
The Oldest Lunar Calendar on Earth – Environmental Graffiti
Leap years explained
Leap seconds explained — USNO
The Y2K Scare
Mayan calendar explained – Calendars Through the Ages
2012 Reality Check — NASA
Series of articles on 2012 by Ian O’Neill on Universe Today
From “The Truth About 2012: The End is NOT Near” by Dr. Ed Krupp from the Griffith Observatory:
- “The Mayan calendar is not spooling up the thread of time. It is coming to the end of a particular cycle in an unending sequence of cycles. According to the rules of the Maya calendar system, a primary interval, Baktun 13, for all practical purposes ends on the winter solstice, 2012. Although pseudoscientific claims have linked this calendrical curiosity to a Maya prophecy of the end of time, there is no evidence for ancient Maya belief in the world’s end in 2012 or even in any unusual significance to the cycle’s completion.The Maya calendar relied on multiple cycles of time. In Maya tradition, these cycles of time run far into the future, and there are ancient Maya hieroglyphic inscriptions that project time into the future well beyond 21 December 2012. At the end of Baktun 13 (a period of 144,000 days or 394 years), a new baktun will begin. There is no Baktun-13 end of time. The notion of a Baktun-13 transformational end of time is modern. It originated in Mexico Mystique, a book published in 1975 by an American writer, Frank Waters, who made computational errors.”

Transcript: Calendars

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Good. I see you’re rested from your exotic cruise.

Pamela: I’m not sure I’d say rested. The thing about vacations is there’s so much to do that you just come back a different form of tired.

Fraser: I think your body is so used to travel that it can’t tell the difference between holidays and going to some astronomy conference.

Pamela: No, that’s entirely true.

Fraser: So for anyone who wonders, we’ve taken our Google plus experiment to the next level, and we’re now recording this episode as a Google plus “hang-out on air,” which means that it’s just Pamela…me and Pamela in this recording, but we’ve got anyone who wants can actually watch us record the episode on Google plus, and then when we’re done, we’ll open it up and let people join us, and we’ll ask questions, and we’re going to record the whole thing, and we’re going to put it on YouTube or something, and so, you know, hopefully, try and make the whole thing a little more interactive because one of the coolest things about doing these hang-outs on air, or the “hang-outs” is that we get to answer questions and meet with the fans. We’re trying to sort of take that to the next level. So in the future, if you miss this one, we’re going to try to move to a regular schedule now where you can know that at a certain time you’ll be able to join and watch us record AstronomyCast, or you can just wait until it pops up in your audio player just like normal. Nothing’s going to change, just more – more better.

Pamela: But this means people can subscribe to our YouTube channel as well as our itunes feed.

Fraser: Yeah, right. It’s going to be very confusing.

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Fraser: OK, well let’s get cracking. So our lives are ruled by calendars and the calendars are ruled by astronomy, so as we near the end of 2011 and get ready to ring in the New Year, let’s discover the astronomy underlying the days, weeks, months, and years that segment our lives. So… I was really worried when I was doing that intro because I was thinking you know this almost starts to sound like astronomy, like, our lives are ruled by the motions of the stars. You know, it’s very “astrology sounding,” so not astrology, but astronomy runs everything.

Pamela: Right, so I mean, if you think about it, there are so many different things — mostly related to agriculture, admittedly — that without knowing exactly what dates the Sun is where, you’re going to end up freezing your vegetables, or not harvesting your wheat on time. So at the end of the day, our nearest star, our sun, rules how we should set up our calendar if we want our calendar to make sense for agricultural purposes, and if you get agriculture wrong, everyone dies of starvation.

Fraser: Right so getting some kind of calendar set up and in place is critical. Some of the things that happened, such as the day and night cycle, are just hardwired right into our evolution, but other things clearly are human constructions. So when did calendars first start to happen?

Pamela: As near as we can tell, there’s always been some sort of a calendar system, but there haven’t always been sensible calendar systems, and the problem that we run into is the Moon doesn’t politely orbit the Earth in an integer number of times every year, and so the easiest way to set up a calendar is to set it up based on the lunar cycles, based on full moon to full moon, or new moon to new moon, but if you do that, your year ends up being about ten days too short and so there’s this problem of “Oh, (insert expletive of choice)! How do we keep our year cycled with the planting season?” So then you have to start inserting leap months, but even if you just come up with some mathematical equation to try and tie it strictly to the Sun, even the planet’s rotation about its own axis isn’t an integer number of days per year, so you still end up with this leap-cycle problem, so basically we’ve always had calendars and they’ve never worked.

Fraser: Always had calendars, and they’ve never worked [missing audio]. So then what are some of the calendars? I mea, what are some of the early ones that people started to use? Because I guess the point being that because they never worked, people have needed to come up with some invention or some solution to solve the problem that Mother Nature doesn’t…you know, didn’t nicely match up the lunar cycles to the solar cycle.

Pamela: So pretty much looking across all the different calendars, you want to look at…we find over and over and over that early calendars tended to be built on the 19-year cycle because the number of lunar cycles it takes to line back up so that you have a full moon with the Sun in place “X,” and you have a full moon again with the Sun in place “X” is about (within a few hours) nineteen years. So culture after culture after culture built a 19-year calendar that was based on mostly having 12 lunar months, but then every few years sticking in some sort of a leap month, so this is just one of those things that everyone seemed to settle down upon in some point in their calendar.

Fraser: And so can you give me some examples? I mean, were there some cultures that used that?

Pamela: Well, we see it, for instance, in the Chinese calendar. This is one of the cultures that continues to use this type of calendar today, where they look at the lunar cycle, but it’s not built purely off the lunar cycle. The Islamic calendar is built purely off the lunar calendar. The Hebrew calendar is sort of-mostly-kind of built off the lunar calendar. And they look at where the Sun is, they look at where the Moon is, and really they’re all kind of complicated — and crazy math.
?

Fraser: [missing audio]

Pamela: Well, I mean, really they just sort of have to do things along the lines of, “OK, so the Sun made it most of the way across this particular constellation, we have a new Moon, so since it didn’t actually make it out of the constellation, we’re going to make this a leap month.” Or with the Arabic or Islamic calendar – it’s based on the first sighting of the crescent Moon each month. And it has to be a physical sighting of it on the 29th, or they assume it’s there on the 30th, and so whether a given month in a given country is 29 or 30 days depends on whether or not somebody saw the moon on the 29th day of the month, and so you end up with all of these things built in that are…it’s kind of head-scratching to try and put it all together.

Fraser: So if you were going to try and develop a calendar, what are the problems, as you say, you know, the problems that needed to be solved? Let’s sort of iterate through them.

Pamela: The primary problem that needed to be solved is each of the different cultures — and this really is a cultural problem — wanted to find a way to have their religious holidays fall at roughly the same time in the solar cycle from year to year. So in the Christian church, it was a problem of trying to figure out how to get Easter consistently about the same time every spring. With the Jewish calendar it’s the problem of trying to get Rosh Hashanah at roughly the same time in the fall. The Arabic calendar…they gave up. They simply cycle through so that every year Ramadan falls in a completely different month compared than the calendar used by the Western world. But many of these other calendars were trying to solve the problem of, “how do we have key celebrations fall during the same seasons that often somehow relate to the holidays being celebrated?” Even our own transition in the Western world, going from the Julian calendar, which dates back from the early 300s — that calendar wasn’t perfect, and Easter was drifting and this was a problem, so they came up with the Gregorian calendar to try and solve the problem of Easter.

Fraser: And so you’ve got this disconnect, right? Between the Sun takes – it doesn’t even take 365 days – it takes somewhere between 365 and 366, the Moon takes 29-ish days to go around, right? So each one of these is some kind of mathematical problem, right?

Pamela: Right, and so with the Moon being 29-ish days, the problem was solved by having months that alternated in lunar-based calendars from 29 to 30 days, and a lunar calendar loses about ten days on the solar calendar every year, so if you throw in an extra month every three years, you can sort of stay on cycle, but that still means that you have that month-long swoosh back and forth for holidays like Easter, so when they tried to come up with a calendar that didn’t have as much movement in it, that was when they took the, “OK, for religious reasons we have a seven day week. OK, so we have a 365-day year, mostly, but it’s actually 365.256363. How do we make up for that?” Well, .25 means, well, the first good mathematical calendar, it meant that every four years you have a leap year, so we developed, initially, the first really good calendar was a 365-day year with a leap year every fourth year, and that made the average year 365.25 days, and so now you’re just missing that .006363 part of the year. Now, while that doesn’t sound like a lot, over a couple thousand years, it caused the calendar to drift enough that Easter was misplaced by about 10 days, or at least the part of the year that was a valid part of the year to put Easter in started to drift, and so they decided in the late 1500s, “Crud! We need to figure out how to fix the leap days so that the year is an even more accurate representation of that 365.256363.”

Fraser: And they had to do some pretty radical surgery to their calendar at that point, didn’t they?

Pamela: Well, it wasn’t that radical except in terms of they had to figure out how to get the two calendars aligned. So the change to the calculation went from being 365-day year with one leap day every four years to a 365-day year with a leap year every four years, unless the year was a multiple of 100 in which case it was a leap year only if it was a multiple of 400. So for instance 1900 wasn’t a leap year, but 2000 was a leap year, so mathematically it didn’t change that month, but the problem was they were off by those 10 days. And so they had a couple of options: they could either have a leap day every year for several years, or they could just suck it up and move the entire calendar, and that’s actually what they decided to do.

Fraser: And that’s what I meant, was they just said, “OK fine, you know, let’s just shift the whole thing ten days. Everybody agree? OK, let’s do it.” You can just imagine the coordination that was involved.

Pamela: The thing was not everyone agreed. This was something that came out of the Catholic church, and when they were sorting all of this out in the late 1500s, it wasn’t a Catholic world, and so when they made the jump, initially only the Catholic European countries made the jump. It took until, well, very recently, actually, before all the nations of the world had finally, mostly, kinda, sorta given in to using the Gregorian calendar.

Fraser: Are there still people that don’t use the Gregorian calendar?

Pamela: Well, so you have to look at, well, what are they using the calendar for? So you still have…the Chinese have the Chinese calendar, the Arabic world still has the Arabic calendar, and all of those different nations are slightly off from one another as well, but for the most part, we finally do have all of the major countries have, at least for financial purposes, adopted it. Turkey was one of the last countries to adopt it, as was China; China adopted it in 1929, and Turkey adopted it in 1926.

Fraser: Are there other motions of the…like of the Earth, like, I know the Earth’s axis kind of wobbles a little bit; it precesses. Would that over long terms as well have an impact on our calendars?

Pamela: Well, the precession isn’t so much of a problem as the fact that the length of the day is actually changing, so as our Moon slowly moves further and further away from the Earth, we’re getting longer and longer days, so we can look back in the historical record, and within the fossil record start getting down to days that were many hours shorter than the current day. So this is where we keep having to add in leap seconds now and then because, well, our rotation rate is changing.

Fraser: And it’s at a level that…I mean, I guess the modern scientific timekeeping devices are so accurate that they actually can do that. And so do they actually do that? Do they actually modify the length of the day every year?

Pamela: Well, they don’t modify the length of the day, but they have been working to try and keep the calendar tied to the Sun, but they forfeited that in 2012, and there’s actually recently an announcement saying that there would be no more leap seconds starting in 2012. The problem that we run into is: modern-day timepieces are accurate enough to notice, “Crud! The Sun didn’t line up with the stars on the exact moment it was supposed to relative to my perfectly precise Atomic clock. Let’s fix this.” But every time they add a leap second in — that wreaks havoc with operating systems the globe over, so trying to push that out to all the cell phones, all the laptops, all of the…every electronic device out there, they gave up. And this is actually starting many different people to try and say, “Well, maybe it’s time to reconsider our calendars yet again.” In fact, there was recently a call put out at an international meeting to change our calendar yet again. Keep the seven day week because people realize there’s just some things that aren’t going to change, and the seven-day week is one of them. But what if we redo the calendar in such a way that every year Christmas is on a Sunday, every year your birthday is on the same day of the week, and we simply re-jigger the year, and where the leap years fall so that we can have this perfectly lined-up perpetual calendar? And the justification that they do for this is, if you think about it, if you work in academics, or if you work in a business that has lots of holidays, just trying to figure out, “Oh, crud! This year Fourth of July falls on day “X.” What day do you give people off? Oh, crud! This year Christmas falls on a Sunday, so we have a different number of vacation days compared to last year.” Lots and lots of time goes into figuring out how to schedule work holidays, how to schedule a lot of different things, so maybe if we re-jigger our calendar so that holidays are always the same day of the month, so that the year always starts on the same day of the week, we can save time on having to re-jigger our work schedule every year.

Fraser: Well, of course, though, I mean, our Thanksgiving here in Canada falls in a completely different month than yours does in the States, so you can imagine it’s a whole other level of coordination and cooperation. Have there been other… I mean, more radical ideas for your calendars? Things that…I mean, do we need to have seven-day weeks, do we need to have…?

Pamela: Well, we don’t need to have seven-day weeks, although it seems to be the right length of period that people are actually willing to work it. If you think…would you want to really work more than five days at a time without getting time off?

Fraser: I’ve been known to.

Pamela: Yeah well, we’ve both been known to, but imagine if that was the expectation.

Fraser: Yeah, exactly. Yeah.

Pamela: But there have been people who’ve moved to say, “perhaps its time we moved to a decimal system, perhaps it’s time to get rid of this whole 12-month thing altogether,” and then the Mayans they took the approach of “we’re just going to number every day.” They have months and all of that stuff as well, but their “Long Count” calendar… they just simply number the days; that’s how they handle it.

Fraser: We can’t talk about calendars in 2012 without talking about the Mayan calendar. How did the Mayan calendar work, then?

Pamela: The thing that’s hard to wrap your head around is their way of looking at numbers wasn’t a base-10 system like we’re used to. Instead they did things in base-18 and in base-20, so their “long calendar” is actually made of looking at all of these different, crazy cycles that take thousands of years to get through, and they just count the days from the beginning of all of it until today, and so the beginning of all of it, we think – it’s always hard looking at archeological records…we think the beginning of everything was 3114 B.C., August 11, 3114 BC if you want to be specific, and it’s simply been counting forward ever since then. And it’s built on a system where they have days, so there’s a one day, and then they have a month-like period which is 20 days, they have a full circle which is 360 days, they have a (I’m going to mispronounce this)…they have a “k’atun,” which is the cycle of all of these days, which is then 7200 days, and all of these cycles come together into the “b’ak’tun” (which I know I mispronounced), which is the culmination of all of these days cycling through, and that longest cycle is 144,000 days long, so there’s 20 days in the first cycle, then there’s 18 cycles of 20 in the second cycle, there’s 20 cycles of the previous one and so it’s…the entire thing is 1 x 20 x 18 x 20 x 20 to get to their calendar.

Fraser: Right. And 144,000 days from when the calendar started happens to sync up, probably, with December 21, 2012.

Pamela: It’s actually 14 times that.

Fraser: 14 times a hundred and…OK

Pamela: Right, and so this is where their myth starts to come in because their myth is: on the 14th of these cycles starting is the day when it goes to the next “b’ak’tun” and so that’s…

Fraser: …the end of the cycle.

Pamela: Yeah.

Fraser: Yeah. Right. And, in our equivalent, that’s because they numbered every day right from the beginning right until now…you know, this would be day 123,692, or something like that, right? That would be the way they would describe a day. That would get very…that would take up a lot of paper, a lot of stone.

Pamela: Well, they actually…because they’re using an almost base-20 math system, it actually ends up being number-number-dot, number-number-dot, number-number-dot, number-number-dot, number-number, which is still a pain, but it starts to…it’s the equivalent of saying the 5th day of the 13th month in the 24th year of the 15th cycle of the 30th cycle of cycles.

Fraser: And so then when this calendar…and so this calendar theoretically runs to an end. Would they…I guess the point is they never planned to be around that long; they never really thought about it, like, it was just…would they just…the whole system would just start again the next day?

Pamela: This is one of those things that we just don’t have the records to tell us. I mean, it’s a cycle, so yes, it does just start over, but I don’t think they’d ever really plan for it to start over, but we don’t really know, and that’s the crazy thing is they don’t have any “world ending” lore tied to this; they don’t have any “everyone’s going to die” lore tied to this — it’s just the calendar, and so it’s…

Fraser: You think about the fact that how, like, computer scientists didn’t really think through the implications of the year 2000, and they only wrote their code 20 years before the end of the century. They never expected that their software would get used for 20 years, or 25 years, “Oh yeah, no, we’ll just put in, you know, ‘87, ’89” — that never really occurred to them. As you can imagine, again going back to the Mayans building this calendar, “Well, are we going to need this in 5000 years? Nah,” you know? It just never came up, so…

Pamela: It’s the millennium bug.

Fraser: It’s the millennium bug, yeah, exactly…so now we’re having to deal with the millennium bug. Thanks, Mayans.

Pamela: It’s just kind of funny that the software programmers and the Mayans only have a 12-year difference in their failure to think through their calendars.

Fraser: To think through the long duration of that…yeah, that’s good. So then, what things would change our calendars? Would there be events? Would there be things that will happen in the far future, maybe, that would change our calendar dramatically?

Pamela: So, we do have slight changes in the equinox positions that do occur, not due to the precession of the pole, but because our entire orbit – it’s not circular, and so as our orbit slowly rotates in combination with the precession of the pole, we end up with changes in equinox, we end up with slight changes in the solstice dates and the spacings of those, and so the slight things add up over time to, again, leap seconds here and there which will eventually, given enough millennia, turn into leap days. So it’s just a matter of our planet isn’t fixed in space; its axis is turning, its date of perihelion is changing, its date of date of aphelion is changing, and as all these things slowly change, they affect our calendar.

Fraser: But that is something that’s going to happen over the course of…

Pamela: Millennium…

Fraser: But that’s still going to be a cycle, but it would be a, yeah, but it would be a bigger cycle. You just end up with the movement of our orbit sort of slowly rotating around the Sun. What about the fact that our rotation is slowing thanks to the Moon? Will we get to the point where days last a very long time?

Pamela: Well, the rate at which things are slowing is such that, yes, it will happen. Our Sun will probably destroy the Earth before we have to worry about it too much. So you can imagine over the remaining course of humanity we might see a five-hour change, but I think that’s the type of thing…there’s already human beings that quite happily run on 30-hour cycles as they work on shift work, so that’s the type of thing we can deal with over time.

Fraser: Evolution can deal with that. And then would there be something that would perhaps, you know, when the Sun turns into a red giant, and…?

Pamela: Yeah, we’re going to have to be on a different planet by then.

Fraser: …the planet’s center of gravity changes, we’ll spiral outward, that’ll make the years longer, right?

Pamela: Yes. Again, we’re likely to be on a different planet, or dead by then, so I’m not particularly worried about the calendar.

Fraser: Right. OK. Alright, alright…just checking. OK, cool! Well, thanks a lot for the calendar info, Pamela. And thanks to everybody who watched us as we did the recording.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 244: Io

admin — Wed, 21 Dec 2011 20:51:17 +0000

If you want to see one of the strangest places in the Solar System, look no further than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometres into space.

Ep. 244: Io
Jump to Shownotes
Jump to Transcript

Show Notes

Google+: Fraser, Pamela
End of the World — Not! Cruise
Images of Io — NASA’s Photojournal
Io, Galileo and Simon Marius — Gish Bar Times
Controversy over the discovery of Haumea – Mike Brown’s Planets
Io exploration overview — NASA
Io in mythology — Wiki
Voyager spacecraft and Io
Galileo spacecraft and Io
Magma Ocean Flows Under Io’s surface — Universe Today
NASA’s Plutonium Production Predicament – Universe Today
Juno Mission

Transcript: Io

Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing?

Fraser: Good. And again, we’re recording well into the future. It’s early December, but we’re recording this for late December because you’re going to be cruising somewhere.

Pamela: Yeah, something like that.

Fraser: Not doing anything?

Pamela: I’m going to be off exploring the planet.

Fraser: You’re going to have a holiday? Sounds good…but once again, we’re recording this as a Google plus hang-out, and so if you want to participate, all you have to do is circle either me or Pamela and then we will give an announcement when we’re going to do the recording, and then you can just jump into the hang-out and we stick around for half an hour or an hour after the recording and answer questions, and it’s a really good time. So I highly recommend it — just circle one of us. And this is kind of cool because we’re recording at a really weird time, and so it’s an opportunity for our Australian listeners to join us on this one.

Pamela: And it just occurred to me we’re recording this a year before we’re going to be on a cruise together celebrating the world not ending.

Fraser: That’s right, or the end of the world — one or the other.

Pamela: Well, yeah…either way, we’ll be together.

Fraser: We’re pretty certain it’s not going to end. Yeah, and so you can go and find out about that at astrosphere.org/endoftheworld?

Pamela: Just go to astrosphere.org. It’s the lead story right now.

Fraser: And there’ll be a link to that. So once again, December 2012, we will…we’re going to be doing a cruise with a bunch of other people, David Brin, astronauts, astronomers… It’s going to be a really good time. So you can check that out on our astrosphere website. We sell it so well. We’ve got a whole year to nag you about this. Actually, you know, I think it’s going to fill up, and we haven’t really publicized it outside of just the AstronomyCast shows, so I’ll probably start talking about it more on Universe Today, so and then it will sell out. I highly recommend you go with us. OK, let’s get on with it.

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Fraser: So if you want to see one of the strangest places in the Solar System, look no forward than Io, Jupiter’s inner Galilean moon. The immense tidal forces from Jupiter keep the moon hotter than hot, with huge volcanoes blasting lava hundreds of kilometers into space. And, Pamela, before we get into this, I have to let you know my daughter proposed tonight’s topic.

Pamela: Yes, she is the one who text messaged me to find out if we could do this.

Fraser: That’s right. So she texted…“Can I text message Pamela?” I’m like, “Yeah, OK.” “I think you guys should do a show on Io.”

Pamela: And I was really confused because I thought she’d written “lol” and lost the second “l” because it was an iphone.

Fraser: No, no, no, she’s ligit. She knows her science; she loves Io.
OK, so then, you know, we got a whole episode to just talk about this moon and, you know, there are so many really interesting things about Io. Let’s get started — and I think, you know, we gotta get started with the discovery. When did we find out about Io?

Pamela: Well, finding out about it…there’s always this lag between discovery and publication. So here we have this interesting…the first dude was too slow, so according to anything you’re likely to read, it was Galileo who discovered Jupiter’s moons in January of 1610. The first night he looked, he probably saw Europa and Io pretty much stacked on top of each other and couldn’t separate them, but then on January 8, he clearly saw the two of them as two distinct objects, and he went on to publish this just a couple of months later in March of 1610. Now the thing is, Simon Morris, another person who’d already figured out how to use telescopes to look up, claims that he saw them in December of 1609. And that would have been one month earlier.

Fraser: Well, where are the photos?

Pamela: Well, yeah, that’s the thing. And he didn’t bother to publish his results, so here’s a clear case of: if you don’t share what you see with the world, you didn’t actually see it.

Fraser: And that has happened even recently with Mike Brown, [missing audio] killing Mike Brown from Cal Tech. You know, people discovering objects and then wanting to gather more science, and then other people figuring out what he’d done and trying to break the news before him, so that still happens. If you discover it, the race is on.

Pamela: Yeah. Publish, publish, publish!

Fraser: So then, I mean, do people have an opinion about whether he really did see it? I guess it really doesn’t matter, right?

Pamela: History gives all the credit to Galileo. And you know Galileo suffered enough for his good work — might as well allow him to keep all the Galilean moons for himself.

Fraser: And so what was he able to see?

Pamela: He saw a small star that appeared to move back and forth beside Jupiter — it was very unexciting. In fact, if you go out with a good pair of binoculars, or a Galileoscope (you can still buy Galileoscopes at Galileoscope.org)…with a Galileoscope, they actually have a lens that allows you to see exactly what Galileo saw, and it’s basically this little, itty-bitty, tiny field of view, where Jupiter is a smudge that you can just make out bands, sort of, on a really clear, perfect night, and then you see the Galilean moons dancing back and forth along a straight line like balls attached to a string.

Fraser: Right, and we’ve talked in other episodes — that was a mind-bending discovery because the previous thought was that everything orbited around the Earth, and here was something orbiting around Jupiter.

Pamela: And Kepler actually proposed that maybe these should be referred to as Jupiter’s moons, and Io being the closest in of the four Galilean moons, that was almost planet #1 orbiting Jupiter.

Fraser: So, then it was just stars and that’s all that anyone could see for years and years and years, right?

Pamela: Yeah, and the thing is all we had was this boring object; it had a great story behind it. While Simon Morris wasn’t credited with his discovery, he did get to name it, and it was named after one of Zeus’ mistresses. This is one of the neat things about the moons of Jupiter is for the most part, they’re people that Zeus seduced at one point or another in mythology. And Io, contrary to the look of the object, Io is named after a female that Zeus seduced and then when Hera, his wife, caught him, he quickly turned poor Io into a white heifer to try and hide what he had done, and there’s all sorts of myths about either the heifer ended up one of Hera, Jupiter’s (Zeus’) wife’s, basically, animals, and all sorts of crazy things, but basically you have this passive little white cow that we eventually found out was anything other than a passive white little moon.

Fraser: Right, right, but then even with better telescopes, over the centuries, we didn’t get much better of a view.

Pamela: No. In modern times, or at least within the past 150 years or so, we were able to make out as we looked at it that, well, it appeared to have slight changes in color across the two hemispheres, and by watching it over time, seeing how the colors varied over time, people were able to figure out that it’s not pear-shaped. Because that’s the thing — when the north and south hemispheres don’t give off the same amount of light, it could either be because, well, the one hemisphere is smaller than the other, like a pear, or it can be, as the case actually is with Io, that you simply have dark splotches, and by watching it as it rotated, they were able to figure out that this is a little, tiny, splotchy something going around and around Jupiter.
?

Fraser: But they didn’t know why.

Pamela: They didn’t know why. That actually took until the 1970s, and the first time we figured that out was when the two Pioneer spacecraft made their way out and in December of ’73 and ’74, respectively. They flew by and it just wasn’t quite what they expected. They found high radiation, they found all sorts of weird materials — it was a silicate world, rather than an icy body. All the other moons that we were looking at, at that point, they were just big old blocks of ice, or big old ice balls, literally, but here they had a silica planet, and…or a silica moon, as the case would be. But the thing was, the Pioneers didn’t actually catch any of the volcanoes going off. For that we’d still have to wait another five years.

Fraser: Right, but I know that the Pioneer spacecraft were fairly low-tech for spacecraft. They didn’t have great instruments; they, you know, they didn’t probably make that close of a fly-by, so we just got a glimpse of what was going on, but I know that it was future spacecraft that really pulled things together.

Pamela: Right, so the next missions where things started to get interesting is actually a pair of missions that I’m just able to remember. Back in 1979 in March, Voyager I flew past Jupiter, and my parents made me take naps so I could stay up to watch the data coming back from the mission. And what was amazing is when they started when Voyager started sending back images, the scientists saw this planet that was covered in these weird pits and discolorations and these mountains and clear volcanoes, and as they went through the data, they were able to catch this amazing, basically, volcanic plume rising up over the edge of this small otherwise unassuming moon when you’re watching it from as far away as Earth, and it turned out this is the most geologically interesting thing that we have in the entire Solar System.

Fraser: And were astronomers, like, at all expecting anything like this?

Pamela: No. No. We had no clue anything like this was out there. It was just one of those things. I mean, there was a prediction from the Pioneer stuff. When Pioneer got there, there was absolutely nothing. So let me step back. From Pioneer there’s absolutely nothing weird anticipated. We’d gotten hints that there was stuff going on from Pioneers, and there had been a theory paper published that predicted that maybe tidal heating could cause some sort of a volcanism, but the level at which this was seen, the amount of sulfur and sulfur-dioxide getting thrown up, the arcs of material going between Jupiter and Io, none of this was predicted ahead of time. And it was like someone had taken every Dark Ages painting idea of Hades and turned it into a moon orbiting Jupiter. All that sulfur, all of that suddenly became real.

Fraser: I mean, I always imagined seeing, like, video of the volcanoes on Hawaii, or some of the…where you’ve got like these fountains of lava blasting in the air, and you’ve got you know, globs of lava, you know, plopping out of the volcano and landing as, you know, chunks of rock around. I mean, you’ve got this world, but it’s that times, I don’t know, like 1000, like you’ve got these streams of lava blasting out of the moon and, you know, creating these fountains of material. So let’s imagine, you know, that we were, like, standing above Io. What would we see?

Pamela: Well, so standing — that doesn’t even give you enough perspective. So, the thing to think about is the biggest volcanic eruption that most of us are familiar with from the news is the unpronounceable volcano that went off in Iceland in 2010, and that volcano threw material several miles up into the air, but it was still “single digit number” of miles into the air. Well, Io is about a third the radius of the planet Earth, not quite, it’s a little bit less than that, and it’s able to throw material into space roughly 1/3 of its diameter, so…[laughing]

Fraser: Hundreds of kilometers…

Pamela: It’s going hundreds of kilometers into space, and we just don’t have the…

Fraser: Well, it’s even more than that, right? I mean, as you said, it’s trailing away from Io itself and being absorbed into Jupiter.

Pamela: Right.

Fraser: It would be like volcanoes on Earth being blasted off and being, you know, making their way to the Sun.

Pamela: Or imagine having a volcano going off and the material in the volcano becomes part of the Northern Lights because that’s a closer analogy to what’s happening, or even better would be imagine if the Earth’s moon suddenly had a volcano that joined the Northern Lights because that’s essentially what’s happening is when these volcanoes go off — some of the material that gets released into the atmosphere, it gets…or not so much into the atmosphere, that gets released into space, it gets caught up in the magnetic field lines and forms these amazing streams of radioactive material that are kind of dangerous to the spacecraft that go through them. But this is plasma streams writ large, where volcanoes, gravity and electro-mechanics are all interacting in violent and amazing ways I don’t ever wish to calculate.

Fraser: No, or visit.

Pamela: Or visit. Yes.

Fraser: Right. And so, you know, we talked about, like, if you could stand on the surface, what would you see?

Pamela: If you could stand on the surface, you’d simply see a volcanic eruption that streams all the way into space. So if you’ve seen a rocket launch, you know how you can see the stream of material going all the way up into the sky and stretching out over the horizon? Well, this is a volcanic eruption that does the same sort of thing.

Fraser: And you would be standing on recent lava flows — no matter where you were.

Pamela: Pretty much. This is a constantly resurfaced world. There are some craters on it, but very few. So the surface is… we’ve seen areas basically the size of Arizona get resurfaced just in the years that we’ve been watching this planet with spacecraft.

Fraser: Wow!

Pamela: I keep calling it a planet – it acts like a planet! It’s not; it’s a moon. So, this moon…

Fraser: Now, when we see the pictures…we’ve seen the pictures from Voyager (and we’ve seen the updated pictures taken by New Horizons and Cassini), it’s got this strange, like, it looks like a bruised orange, like, it’s got these yellows, and oranges, and browns, and all these crazy colors, so what’s going on there?

Pamela: Well, the yellow is sulfur, so this really is every imagining of Hades turned into a moon. So, you do see when you look at the images some ices, you do see variations of the sulfur, where you get irons and you get different silicas mixed in, but that overwhelming yellow covering the whole moon — that’s just sulfur and sulfur-dioxide.

Fraser: Is it like snow, or…?

Pamela: No, think of it as they talked about with the unpronounceable volcano that went off in Iceland. All of the silica ash that would destroy airplanes if airplanes flew through the ash — well, that yellow-y stuff that you’re seeing is similar sorts of material. It’s all the silica stuff that got thrown into space, all the sulfur ash that got (I don’t know if ash is the right word), all of the sulfurs that got thrown into space, and then, gravitationally, some of it gets pulled back down — a lot of it gets pulled back down, and it’s kind of amazing the size of the arches that some of these plumes make as they go up, and then fall down far away from their volcanoes.

Fraser: And, uh, someone from the hang-out wanted to know: why is there so much sulfur?

Pamela: You know, this is actually one of those things that when I was researching for this show I was trying to find. I couldn’t find a quick answer anywhere. This is a world that has a disproportionately large amount of silicon, a disproportionately large amount of sulfur, and its composition is just different from everything else, so somehow when the Solar System was differentiating, this one rock ended up in a part of the Solar System that for the most part is ice and gas.

Fraser: And, so then what…and then what is causing this? I mean, now those regular listeners to the show will know, but I think it’s quite an amazing story. So what is causing this moon, unlike all the rest, to be so volcanically active?

Pamela: Well, it has an unfortunate location. So, as I was saying earlier, it’s one of the four Galilean moons, which means it is orbiting Jupiter and it’s the inner most of those four, and the others are Europa, Ganymede and Callisto, and the inner three: Io, Europa and Ganymede have orbits that have, over time, settled into what’s called a resonance. So for every two times Io goes around Jupiter, Europa goes around once, so if Io’s at the top of Jupiter and Europa’s at the top of Jupiter and you’re looking down from the north (so that’s kind of a weird way to think of it), you’re looking…you’re hovering above the north pole, looking at the planet, and at the top of the planet, you see Io and then directly above it you see Europa, then the next time Io gets to the top, Europa’s going to be exactly at the bottom. Now, Ganymede is doing this exact same thing, but for every four times, so every time that Io and Europa are lined up, Ganymede’s going to be lined up with them, and this resonance: this 2:1, 4:1, 1:1 resonance between these three moons forces Io to sometimes be closer to Jupiter, sometimes be further from Jupiter, and to undergo constantly changing gravitational pulls, and this constantly changing gravitational pull has the effect of, over and over and over, squishing Io like a stress ball held in the hand of an angry Roman god, which according to mythology it is [laughing], so…or in this case, yeah, I’m not going to go into the mythological connotations on this one.

Fraser: But it’s that squishing, and then un-squishing, and then squishing, and then un-squishing — just heats it up, and there’s, I mean there are so many examples that you can think of something very similar. You can take a rubber ball and squish it and un-squish it.

Pamela: If you have a small child that you want to tire out, hand them a small rubber ball and have them bounce it over and over and over with a paddle, and eventually, it will actually change temperature from doing this.

Fraser: Yeah, I mean, bounce it up and down for a while, and then touch it, hold it, and you’ll feel the warmth coming off of the ball and that’s because it’s the same process.

Pamela: In this case, this constant squishy-squishy-squishy that it undergoes is able to build it up to a temperature of 1200 degrees, and it’s estimated that anywhere from 20% or more of its mantle is melted and that there’s a vast subsurface — basically, oceans of lava. The surface is probably about 7 miles (12 km) thick, or more. It’s at least that thick, but it’s certainly not more than 25 miles (40 km) thick, so this is a world with a very, very thin surface over a rather hot interior of magma, and all of that’s just under pressure waiting to break through and fly hundreds of kilometers into the atmosphere.

Fraser: Right, and so it’s that tidal forces that…well, I guess it’s a mixture, right? The tidal forces are creating huge pockets of this liquid that’s increasing the pressure, and then at some point it has to find a way out, and you get these cracks in the surface, and you get these geysers, and then at the same time it’s a smaller object than Earth and so it’s got less gravity, and so things can just fly further when they blast out.

Pamela: Right, and what’s kind of awesome is not only are there the volcanoes, but there’s also regularly-formed mountains from all of the forces that the crust is undergoing from having all of this squishing, all of these tidal forces, all of the pressure from the magma, and some of the mountains that are forming are actually bigger than Earth’s Mt. Everest. So here again you have something a little less than a third the diameter of Earth, mountains bigger than Earth, volcanoes spewing material up to what on Earth would be the orbital height of the Space Shuttle — I mean, just imagine if one of the volcanoes in Iceland or Indonesia or Hawaii went off and hit the Space Station! That’s the scale that we’re looking at here!

Fraser: And again, like, I think about how you’ve got Europa, which is a little further out, which possibly has, you know, a crust of ice with liquid water underneath, and it’s that tidal flexing has made the water liquid. But with poor Io, it’s the tidal flexing has made the rock liquid. It’s just a different sense of scale. Now, you know, we always think: Europa, Callisto — maybe there could be some life? Enceladus? What do you think are the chances of finding life on Io?

Pamela: You know, I think if we’re going to find something with something more than a few cells inside, Europa’s the place to look. But Io…we find out at Yellowstone, here in America, all of these amazing thermophiles that live in the hot springs, that live in the extremely sulfuric acid-rich pools, that live in these bizarre chemistries, and these bizarre chemistries are at a completely different pressure and gravity than Io, but compositionally, they’re just as toxic, and if stuff can live in those toxic environments on Earth, there’s no reason to think that stuff couldn’t evolve to exist in the similarly toxic environments on Io. You have a thermal gradient, you have presumably some sort of liquid (that part we don’t know for sure), but you’ve got that thermal gradient and that is one of the things that drives the chemistry of life.

Fraser: Yeah. I mean, if you’ve got a source of energy, that goes a long way… You [missing audio] in helping out life, so it’s really interesting. Now are there any plans to re-visit Io?

Pamela: Well, we want to, and this is one of the problems we’re dealing with now.

Fraser: Yeah, you and I want to. We want Io visited, but…

Pamela: [laughing]

Fraser: Are there any plans by you know scientists? Perhaps space agencies?

Pamela: One of the problems we’re dealing with right now is lack of funding, and this gets reflected in two fairly significant ways. One of them is we just don’t have any more of the radioisotope-driven engines that you need to go out and explore these distant locations in the Solar System; we just don’t have the radioactive materials we need to build more of them. And Congress cut the budget to turn on the facilities necessary to manufacture those radioactive isotopes. And then there were plans to explore the moons of Jupiter in greater detail, but that spacecraft doesn’t necessarily look like it’s going to happen anymore. As they cut more and more of the U. S. budget, as we move toward having our own form of austerity measures, we’re losing our scientific dreams, and so I have to say probably not in the next 10 years is anything going to launch to explore these moons. Now, we do have a spacecraft on the way out to Jupiter; this is Juno. Yeah, so Juno’s going to do a great job at what it does. It’s going to be mapping the magnetic fields of Jupiter, and it’s that magnetic field that carries around the radioactive materials. It’s going to be doing a great job measuring the composition of Jupiter’s atmosphere, and mapping out the gravity of Jupiter. It’s going to do some really awesome things, but this isn’t an imaging mission. It does have a camera on-board; it’s a camera designed to take pretty pictures because we want pretty pictures, but it’s not really a science camera. So the science is going to be the type of stuff that makes the scientists happy, but doesn’t necessarily end up on the nightly news. And so Jupiter is going to reveal a few more secrets, but not necessarily a few more pretty pictures.

Fraser: Oh, wow. OK, on that sad note…well, thank you very much, Pamela, and we’ll talk to you after Christmas.

Pamela: That sounds great, Fraser. I’ll talk to you later.

Fraser: Alright. I hope everybody has a great Holiday, and we’ll talk to you again next week.

Pamela: Sounds great. Happy Holidays, everyone.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 243: Tunguska Event

admin — Wed, 21 Dec 2011 20:34:00 +0000

On June 30th, 1908 “something” exploded over the Tunguska region of Siberia, flattening thousands of square kilometres of forest, and unleashing a force that rivalled the most powerful nuclear weapon ever detonated. What was it? What could unleash that kind of destructive energy? And will it happen again?

Ep. 243: Tunguska Event

Show Notes

Google+: Fraser, Pamela
Images of Tunguska
Leonid A. Kulik — Virtual Exploration Society
Tunguska Blast Still a Mystery 100 Years On — CNN
Tunguska Event Caused by Comet – Universe Today
Book: 100 of the World’s Greatest Mysteries
Tunguska Event -- World Mysteries.com
Was the Tunguska Fireball a Comet Chemical Bomb? — Universe Today
Tunguska Event overview — The Planetary Society
Lake Cheko and the Tunguska Event – National Geographic
Nikola Tesla and Tunguska – Cracked.com
Torino Scale (Ep. 242)

Transcript: The Tunguska Event

Pamela: I’m doing well. How are you doing?

Fraser: Doing really well. We’re actually ahead of time now. We’re actually recording in early December shows for mid-December and even late December, and that is how dedicated we are to getting this show back on track. We’re serious, we’re serious; we’re sorry, and we’re way ahead of schedule now.

Pamela: Yay!

Fraser: And as always we are recording this episode as a Google plus hang-out, and so if you want to participate in a live recording of AstronomyCast, all you have to do is circle me or Pamela in Google plus, and then we’ll, sort of, make a mention of when it’s going to happen, and then you can jump in and join the hang-out and ask us questions and watch us record the show, and then stick around afterward and we’ll answer questions until we’re tired. So super-fun, but you gotta be in Google plus to do it. OK, cool. And so today’s episode was…came from a fan, and they said they wanted a show on Tunguska and – sorry, I don’t remember who it was, but um, I remember someone asked for it, and we said that sounds like a great idea

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Fraser: Ready to roll?

Pamela: I hope so.

Fraser: OK then, so on June 30, 1908 something exploded over the Tunguska region of Siberia flattening thousands of square kilometers of forest and unleashing a force that rivaled the most powerful nuclear weapon ever detonated. What could release that kind of destructive energy, and will it happen again? So Pamela, can you, like, set the stage and tell us about this unbelievable event that happened in Siberia?

Pamela: Well, it was an otherwise perfectly normal summer in an utterly isolated part of the world. This part of Siberia — it’s north of Lake Baikal which is one of the clearest, cleanest lakes in the world, an area where there were still people who lived by herding reindeer to eat — no real cities, no real anything, and out of nowhere at 7:14 in the morning, something streaked across the sky, reportedly as bright as the Sun, and then exploded knocking people off their feet, breaking windows. The shock apparently reverberated such that it was detected as far away as Britain, and the thing was, this was World War II (editors note: World War I) time period, this was right before the Russian Revolution, and no one really actually went to see what all the fuss was caused by.

Fraser: For, like, years…

Pamela: For years…it wasn’t until the 1920s, and this to me is totally crazy because looking at the various reports, people were talking about the sky glowed at night for a couple of nights, observatories all the way around the world reporting that the opacity – how much light is transmitted through the atmosphere, the atmospheric transparency — was for months after this was worse than it had been in the past due to all the dust in the atmosphere. The entire planet knew something had happened.

Fraser: And so you say that it took a little while, but an expedition was sent to find…and what did they find?

Pamela: Well, they actually found the weirdest pattern of tree destruction ever known to mankind. So in 1921, using what is perhaps the strangest logic I’ve ever seen to fund a scientific expedition, Russian mineralogist, Leonard…I wish this was written in Cyrillic because then I could pronounce it correctly, but written in English it looks like it’s Leonid Kulik went, and he said to the government — this is coming off the heels of many wars, “Hey, it’s possible that an iron meteorite crashed in Siberia; we can use the iron for industry. Can you fund me to go look?” Now, here’s the thing: most meteorites that are found aren’t that big. It wouldn’t have been enough to do significant industrial work with, but it was still enough of an argument that they got the money they wanted, so this poor man took the train all the way across the country, found guides to guide him through the woods, got to the point where superstition said, “We’re going no further,” found a different group of guides to take him through the woods, and he found this area where there was essentially a swamp with a bunch of perfectly upright trees surrounded by a bunch of trees that were pushed over, sort of in a bull’s eye pattern with the pushed over, they were pushed away from the bull’s eye, and the bull’s eye, you can imagine, are the trees still pointed straight up. All the trees are scorched, and the ones in the center of the bull’s eye have all of their leaves, limbs lopped off, and all around are all of these bog pits that, at the time, he thought might have been caused from debris from an exploding meteorite.

Fraser: And so, you know, if you haven’t seen the pictures, you really should take a look at them. You know, the only thing that I’ve seen that even kind of compares is the destruction after Mt. St. Helens, where you have these slides, where you have just these trees that are completely flattened in all directions, but you can just imagine…and so the…like, how much space was flattened?

Pamela: The entire area of damage was over 800 square miles, so this is a fairly significant area.

Fraser: Yeah. Yeah.

Pamela: So roughly a little under 30 x 30 square…30 x 30 miles is the way to think of it — under that, but that’s like the size of a good-sized town, city.

Fraser: Yeah, and so OK, so then he finds this evidence, and then what does he do? No sign of the rock?

Pamela: Well, he went home because he had to [laughing], but once he got home, he sought funding to go out and do things a little bit more rigorously. So, when he first got out there, there were all these what he called pothole bogs, all of these – it’s basically swampy areas, and there were all of these places where there were these deep areas of bog, for lack of a better term, pothole bogs is what he called them, and he didn’t have the tools to excavate down into any of these, and so he went back, he got the money to do that, returned and started draining swamps in hopes of finding the meteorite at the bottom of the swamp. So here he is — huge region of damage, in the center is this one bog that he decides this must be the impact bog. It’s in “ground zero,” basically, from the destruction. He drains it out completely, and the only thing at the bottom of it, unfortunately, was a just a tree stump. So, that was rather unexciting. So, now he has this really weird situation where there’s 830 square miles of damage (that’s over 2000 square kilometers for those who are thinking European units, or actually units of everywhere except for the United States), and with all of this destruction, there’s no crater that they can identify, and this was completely mystifying to scientists of the time.

Fraser: Right, because they were starting to understand that some of the craters that they were finding on Earth, and the ones that you can see up on the Moon are, you know, were impact. They thought they were volcanism, but now they’re starting to discover that they’re from these impacts. So that made sense, but yet where’s the crater?

Pamela: Right, and so here they had this mystery. So, trying to figure out what it was, they started off with ideas like, “Well, maybe it was a meteorite that exploded in the atmosphere,” and so that was one of the models that people were working with, and another model (this one was put forward by Fred Whipple in 1930), he suggested that maybe it wasn’t a meteor, maybe it was actually a comet coming in and maybe the comet just happened to melt, ionize, blow up, whatever term you want to give to the transformation of comet to ionized material, water, and dust in the atmosphere, maybe that’s what happened instead.

Fraser: So, why, I mean, why wasn’t there a crater? I mean, wouldn’t you expect that there would be a crater every time?

Pamela: Well, if an object particularly big comes through the atmosphere, the expectation is large things — and this was estimated to have enough material to generate an explosion roughly 5 times the size of the explosion in Hiroshima, so this was a lot of energy… It was figured this was a several-meter-across object. How many meters might add a couple factors of 10 depending on what the composition was.

Fraser: Right, if it’s made of metal it’s one thing. If it’s made of rock, it’s something else, and if it’s made of snow, it’s something else.

Pamela: Right, but the expectation was something with that much energy probably would bring something through the atmosphere. Now, what’s been interesting is to watch over the past more than 100 years now since this event took place, how our ideas have changed. This is one of my favorite things to look at because I remember, just as a little kid, I had a book on this, like, “World’s Greatest Mysteries.”

Fraser: Me too! I think I took it out from the library, and it was like “What Caused the Event?” and we’ll get to the crazy theories in a second. I wonder if it was the same book. That’s funny!

Pamela: It just might have been.

Fraser: You and I both gravitated to the library, grabbed the same book, you know, half a world away. Yeah.

Pamela: I remember sitting on the floor between my bed and my window, like kind of hiding, reading the book with all the scary monster stuff, ‘cause like Loch Ness monster was also in the book I had, and it was just these pictures of all these trees destroyed and everything, and back then they were like, “Well, it was probably this, but there’s no crater. It was probably a meteor, but there’s no crater, but some people think it might have been a comet.” And today we think we actually understand what happened. It’s neat looking through the history.

Fraser: My book was a lot less rigorous than yours because mine went into the crazy ideas. So maybe we’ll get to that later on and dismiss them all. Mine also included black…microscopic black holes, and UFOs and all kinds of…so anyway, we’ll talk about that later, wormholes and stuff…let’s go to the realm of reality here, so please. Sorry.

Pamela: So in 1978, astronomer Lubor Kresák, um, pardon pronunciations again, he actually made the really astute observation that the Tunguska event happened at the height of the Beta Taurid meteor shower. So, this particular meteor shower was caused by Comet Encke, and he proposed that maybe this was a fragment of the comet that we just didn’t realize there was a big ol’ chunk still hanging around, and this big ol’ chunk decided to come through the atmosphere and aim itself at, well, Tunguska. And when they looked at the most likely path through the sky, based on the reports, when they looked at the timing and everything else, this kind of seemed to make sense. And over the past several years, people have done a variety of different things trying to look at chemicals in the area and different…what’s the mineralogy in the sediments, and all of these different things trying to figure out, “Well, what’s the answer?” And it’s gone back and forth from meteor to comet, meteor to comet every few years. So, in the 1990s there were some Italian researchers that looked at tree rings, and they looked for the particles that were trapped in the tree rings that grew during 1908, and what they found was that there was a lot of material commonly found in rocky asteroids, but that is found, albeit rarely…but is found in comets, so that pointed the finger at asteroids — wasn’t conclusive — points the finger at asteroids.

Fraser: So, like, it sprinkled the region with asteroid dust, and then the asteroid dust got incorporated into the trees as they grew? Hey, that’s cool. That’s really clever. Clever scientists…

Pamela: [laughing] So, this is basically the same thing as the KT Boundary only much, much smaller.

Fraser: In trees, yeah.

Pamela: But the thing is they had all of these different data points they had to explain as well. So they had be able to explain what was up with the noctilucent clouds, the glowing skies, all of the material in the atmosphere, and all of that pointed towards a comet exploding and blowing all of it’s materials into the atmosphere, and what was interesting is the reports for what was seen in the atmosphere actually matched the phenomena that we associate with the exhaust plumes of space shuttles launching at night, so there’s this new finger that points instead at comet, probably. Then in 2010, Vladimir Alexeev, they went and used ground-penetrating radar to look at the region, and what they found was it looked like there’d been some sort of a violent impact. They found a layer of permafrost on top — it’s Siberia, it’s cold, it’s still cold…that may be changing; beneath it were damaged layers of materials. So this was the shock wave hits everything and it…what happens when a crater forms is the material goes up, the material from inside the crater gets pushed out of the way, you have the fragments of whatever made the impact comes in, and then the material that got thrown up settles back down on top of it. So you can actually flip the surface material upside down in the process of forming a crater, and so when they used their ground-penetrating radar, they found this evidence for what looked like, well, no large rock, but none-the-less, shredded asteroid. Now, one of the weird things I can throw in that goes into the I-don’t- know-if-it’s-true-or-not-but-there-was-this-guy category is I was actually a foreign exchange student in the Soviet Union back in 1991, and I was studying at the Six Meter Observatory in the Caucusus mountains, and I met one scientist who had a small jewelry box with like the cotton that you usually get a necklace on in it, and on top of it was this really weird shard of material that he said was slightly radioactive, and he claimed was a shard from the impact at Tunguska, and I remember thinking, “I don’t know if this is a crazy dude or not,” but it’s something that I still remember.

Fraser: Well, and I think that there’s been some recent discoveries of hybrid asteroid-comets, so you know, so it’s not necessarily that anything is just an asteroid or just a comet now. You‘ve got these, you know, much more mixed-up, you know, snow and ice and rock and dirt, you know, everything, and so that, I think, really starts to blur the line, but it could be anything. And I know there was a really interesting…well, we were actually at the AAS — I think it was in Austin. There was a really great… someone had done a really beautiful simulation of an event, and showed almost perfectly these really amazing almost funnel-shaped impact where it airbursted, but it was almost like a gun, and it just shot the force straight down through the atmosphere creating a kind of pattern that we saw, and it really did sort of explain it, you know, that a lot of it just comes down to the angle, the speed, the direction of the Earth, the direction of the object. You get the right combination of factors together and you get this really interesting pattern. It’s interesting. I mean, it makes you think that maybe there were a lot more impacts that we just weren’t even aware of.

Pamela: The things is that…

Fraser: Maybe these are more common than we think.

Pamela: Yeah. The more I read, the more I keep noticing this sentence that’s just sort of tossed in there, over and over I keep seeing the sentence that, “If these occurred over the ocean, prior to the 60s and 70s prior to when we had satellite monitoring, no one would have noticed.” And, you know, that’s true. Most of our planet is ocean and no one would have noticed. And there’s lots of other places no one would have noticed. Deserts…

Fraser: Like Siberia…

Pamela: Well, Siberia, but there the trees get knocked over. But if you think about some of the deserts, no one would notice; prairie — unless you set it on fire, no one’s going to notice, so we’ve got all of these places where you just don’t notice. Now, one of the more intriguing things that I found looking up this story was there’s a lake north of where Tunguska took place. It’s about 8 km away; that’s, I think, about 4 miles away, and it was realized, you know, this lake it’s the right shape to be a crater, but it’s a lake, so they then had to go and measure it, and when they measured it and they looked at the thickness of the silt, the thickness of the silt corresponded to a lake that was only a couple of hundred years old, about how old it would be if it were formed by the Tunguska event, and when they mapped it out, it was crater shaped, and they found evidence from magnetic detections for a rock in the bottom that is about a meter in size and could have made sense if you had some sort of an exploding object. I mean, who knows how it’s going to distribute itself everywhere?

Fraser: Yeah, and I mean, with the evidence the impact actually jumbled up the terrain, it could have created new lakes, and hiding the impact all over the place, so that’s pretty neat. So, OK, so let’s go back to some of the crazier theories.

Pamela: [laughing] You just like this!

Fraser: I can’t wait. So, I’m trying to think…so microscopic black hole?

Pamela: No.

Fraser: But, why not? You can’t just dismiss it outright.

Pamela: So microscopic black hole…in general, it’s just not going to produce enough energy. I mean, that’s the thing about microscopic black holes is if [missing audio] one – yay! Great! We give Hawking a black hole because we finally observed one, and it’s going to evaporate. So, I’m not worried about a microscopic black hole.

Fraser: Right, and if…and so a microscopic black hole would just probably just pass right through the Earth and maybe interact with the occasional atom, but probably not, just go straight through to the other side.

Pamela: And, I mean, the thing is if it was a microscopic black hole, and it wasn’t one that happily, spontaneously evaporating over Siberia, if it was passing through, there would have been an exit event. We would have seen something on the opposite side of the planet along some sort of a vector.

Fraser: A crashed alien spacecraft?

Pamela: Yeah, no. We would have found it.

Fraser: Well, what if it was a crashed alien spacecraft made of rock and ice and dirt…

Then it’s not exactly going to stand up real well to the vacuum of space.

Right, OK. Alright, I’m trying to think, what were some of the other…if anyone in the chat room remembers — some of the other wonky theories…what are some of the other crazy theories that you’ve heard of?

Well, my favorite wonky one and I think this is because I watch “The Sanctuary,” which…I’m a connoisseur of really bad sci-fi shows, and I’m a fan of “The Sanctuary” and it qualifies as really, really back science fiction, and it has Nikola Tesla as one of the, like, characters in the show, and so that’s long lead-up to one of the theories is that it was caused by, I’m going to mispronounce this, the Wardenclyffe Tower, that was basically a giant Tesla coil that Nikolai Tesla had commissioned to be built, but they ran out of money before it was ever built, so one of the theories is somewhere there was one of these things built and Nikola Tesla was doing an experiment, and this caused it.

Fraser: And the field got away and detonated over Siberia, or he was building it in Siberia.

Pamela: It was just the field got away [laughing].

Fraser: Or anti-matter, right?

Pamela: Anti-matter, that’s true, but how did it get there without interacting with something else?

Fraser: Right, like the atmosphere, or dust, or the solar wind, or anything…yeah, yeah.

Pamela: Yeah, unless it’s carrying its own containment field that spontaneously broke up, which is another way of saying alien spacecraft. It wasn’t anti-matter.

Fraser: Well, that was cool, so I guess the one last thing is we talked about the Torino Scale last week, and I guess, this would be…someone mentioned that this would be a “seven” on the Torino. This would be a regional event with absolute certaintly,

Pamela: Only if we detected it first.

Fraser: Yeah, like a half an hour before, “Seven!”

Pamela: And the thing is, things like this are predicted to be happening every…people debate whether it’s every fifty-ish years, or every 300-ish years, so somewhere between those two very different numbers, but these are still time scales of humanity; these are still time scales of civilizations, and so this is the type of thing that could be happening fairly frequently, and we just don’t know it because, well, we’re mostly made of water and our planet is mostly made of water.

Fraser: Right.

Pamela: Or covered in water, it’s not made of it.

Fraser: Right, but were this to have hit Paris, or Moscow, or New York…

Pamela: Bad!

Fraser: It would have been…yeah. I mean, the damage would have been catastrophic.

Pamela: Instead it killed a few reindeer, which is bad, but differently bad.

Fraser: Which is bad, and probably some people somewhere in that region, but [missing audio], but it would have been just probably the worst disaster in natural disaster in modern history. It would have been horrendous.

Pamela: It would have rivaled Haiti, and Chile, and some of the other big earthquakes.

Fraser: The tsunami…

Pamela: I don’t think it would have been as bad as the tsunami was. That was horrible over a much larger region than 800 square miles.

Fraser: So, you know, the good folks who are working on the various missions to search out and find various asteroids – thank you very much! Keep at it!

Pamela: LINEAR, LONEOS, Near-Earth Objects Survey (CINEOS) …we’re looking at all of you.

Fraser: Right. Alright, well thanks a lot, Pamela.

Pamela: My pleasure.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 242: Torino Scale

admin — Tue, 06 Dec 2011 03:16:35 +0000

When you hear of a looming asteroid strike, do you wonder what to do? Should you go into your underground bunker, evacuate the state, or leave the planet? Fortunately, astronomers have developed the Torino Scale – a handy measurement that incorporates both the risk of a strike with the amount of devastation.

Ep. 242: Torino Scale

Show Notes

Google+: Fraser, Pamela
NASA’s NEO Program info on the Torino Impact Hazard Scale
Current Impact Risks (as of this recording)
Asteroid 2005 YU55 — Universe Today
Richard Binzel: Three Questions on Near Earth Asteroids — MIT
News story from 1999 detailing the Torino Scale — Terradaily
1/2mv^2 — Kinetic Energy
The Torino Scale — Universe Today
Torino Impact Scale Explained — NASA
What Damage Have Meteorite Impacts Done in Human History? – Oberlin College
Chíing-yang Meteorite Shower of 1490
Campo del Cielo Meteorites
Tunguska Impact -- Science@NASA
Barringer Crater (Meteor Crater)
Predicting Apophis’ Encounters in 2029 and 2036 -- NASA
AstroGear

Transcript: The Torino Scale

Ep. 241: Astrophotography, Part 3: Image Processing

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Good! So once again, we’re recording AstronomyCast live as a Google plus hang-out, but we’ve muted them all so you can’t hear any voices. Everyone’s going to wave in silence. So if you want to join us for future recordings of AstronomyCast, all you have to do is join Google plus and then circle me or Pamela, and then when the hang-out is kind of approaching, we will…

Pamela: …warn you!

Fraser: …mention it, warn you, and then we’ll start the hang-out up, and it’s kind of a race to get in, but it’s super-fun, and then we try to leave the hang-out open for another half hour, forty-five minutes after we do the recording, and we answer questions and yak about space and astronomy and photography, dogs…

Pamela: Stuff.

Fraser: Yeah, so it’s awesome and super-fun, and we’d love to have you guys join us. So when you hear of a looming asteroid strike, do you wonder what to do? Should you go into your underground bunker, evacuate the state, or leave the planet? Fortunately, astronomers have developed the Torino Scale, a handy measurement that incorporates both the likelihood of a strike, and the amount of devastation. This is good; this was needed for a long time, you know? The Torino Scale?

Pamela: Well, I’m not sure it’s needed so much as it’s just one of those things of die/not gonna die, and probabilities.

Fraser: I mean, that was my intro, right? Asteroid YU 2005 is going to strike the Earth, you know? I gotta know! Should I evacuate Europe? Should I leave the planet? Or is it sort of no big deal, I’m just going to get out my binoculars and watch it strike the neighboring city, so um, you know? So, I think, now we’ve really got a really precise way to be prepared. So where did this concept come from?

Pamela: Well, back in the 1950s, as we started to realize more and more and more that our planet is kind of covered in asteroid impacts, people started thinking, well, so what do all of these different types of impacts mean?” And, well, any time you get scientists thinking hard about something, they’re going to end up coming up with a numerical way of quantifying all of it.

Fraser: Right, like the Richter Scale…

Pamela: Right.

Fraser: Oh man, what is it? The Fuji…F-Scale for tornadoes? The scale for hurricanes…

Pamela: Right, so we have all these different scales, and it was finally professor Richard P. Binzel, who (he was working at MIT at the time)…it was only in 1995 that he presented this at a conference, and so this is a fairly new way of looking at the Universe and saying this is numerically quantified how it’s going to destroy us, and he gave his presentation, actually at a UN-hosted conference, where they were discussing future destruction of the planet Earth.

Fraser: Right, right I, again, you can just imagine scientists going, “Is there some way we can put a number to this?” You know? So right, OK, so he presented, he sat down and decided he was going to be the one to come up with a name, but it doesn’t have his name.

Pamela: No, that’s actually one of the things about it that, to me, was kind of confusing until I realized it ended up getting revised in June 1999 in the Italian city of Turin, which if we weren’t Americans, we would call the city of Torino. So it’s named after the city where the current version of it, more or less – it got revised again later to make it more press-friendly, but it got named after the city where the current, all-but-final version of it was invented.

Fraser: Right and that sounds like a nice, sort of, way to sort of cap it off, and then we’ve got this nice measurement scale from this point on, and it’s actually taken off pretty well, I mean, I can…that’s in my time. When I started Universe Today back in ’99, I can kind of remember when they started to incorporate that scale, and we’ve been watching it ever since. And now, every asteroid that has any kind of likelihood of hitting the Earth gets, you know, will get a measurement on the Torino Scale.

Pamela: And what’s interesting is you might be one of the reasons why in 2005 they felt the need to re-change some of the wording. So this is a scale that goes…

Fraser: Me? What?! What?!

Pamela: Well, it’s a scale that goes from 0 to 10, and it used to be that objects that were Torino level one, which the official definition is “a routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger.” It goes on a little bit longer than that…

Fraser: We’re going to go through the scale in a second, but yeah.

Pamela: So, this is now called “normal,” so anything Torino level one is “normal.” Well, it used to be that it was “events meriting careful monitoring,” and so many members of the press went a little nuts — not saying you’d go nuts, but you’d probably mention it anytime something got a Torino level of one, that they’re like, “OK we’ve got to rename this so people don’t panic.” So in 2001, it went from “merits careful monitoring” to “normal.”

Fraser: Well, and the thing is if you go through enough of these, you see the way it always plays out, which is that somebody discovers an asteroid, they quickly assign a Torino Scale to it, and then, you know, and then everybody points their telescopes at it and gets careful data on it, and then, always, every time so far, the Torino…it just drops back off the Torino Scale because they now know that it’s not going to be any kind of risk, but there’s this gap where the press goes bonkers, and people freak out.

Pamela: Well, it’s fun!

Fraser: It’s fun?

Pamela: Well, I…think about it. We live in a world where people celebrate death and destruction, and pepper spraying, and all these other crazy things that make it into the news. If it bleeds, it leads, and destroying of the planet counts as bleeding.

Fraser: Right, it is big news. Although people gotten a lot more used to it, I’m still waiting for people to get numb to asteroid discoveries and asteroid risks, and they still don’t. I mean every one of them – we had a huge boost when, what was it? 2005? huge boost of traffic to the Universe Today because everyone was searching for it. OK, so then what is the purpose, like, what does the Torino Scale measure?

Pamela: It’s sort of the planetary risk level for asteroids the way we have a color system to describe nuclear threats, the way we have a color scale to describe airport safety threats, it’s just another one of these three-minutes-before-midnight threat assessments, so if it’s zero, we’re good. It’s going past the Earth, we’re fine, just smile and watch — and ten is we all die.

Fraser: We all die. Right, but the point is when you think about the Fujita Scale (thank you to the people in the hang-out who reminded me of the name), but when you think of the Fujita Tornado Damage Scale, you have like speed of winds, and the size of the tornado itself. When you’re thinking about the scale for the hurricanes, you’ve got, sort of, the speed of the winds, and that’s just it, right? When you’ve got the Richter scale, we’ve got the amount of shaking, so what are we measuring with the Torino Scale?

Pamela: ½MV squared.

Fraser: Right, ½MV…right! So we’re measuring the momentum of it?

Pamela: Well, no, no, no — momentum is mass times velocity. This is energy.

Fraser: Right, total energy.

Pamela: So, we have to worry about what’s its mass, what’s its velocity as it’s coming towards us, and it also has to deal with, in addition to these measurable things, it also has to deal with how likely is it that those measurable things are going to impact their energy, well, on our heads.

Fraser: So Jupiter is going to have a lot of mass and velocity, but it isn’t going to hit us.

Pamela: And at the end of its day, its velocity really isn’t that bad, so… It just has a giant mass that isn’t going to hit us.

Fraser: Right, right. It isn’t going to hit us, and the trick is if they hit us. So, it’s both the velocity and the mass of the object, but also that probability of whether it’s going to hit.

Pamela: So, we have things that have high probability, low mass, low velocity, do zero damage; things with high mass, high velocity that are somewhere else in the Solar System and aren’t going to hit us and thus do no damage, but it’s the things in between with a moderate probability of hitting us, and enough mass and velocity to make it through our atmosphere — those are the interesting things that we like to look at.

Fraser: Right, and I know that the danger on the Torino Scale — it could be a high probability, but not a lot of damage, and it could be the other way – a lot of damage, but a low probability of hitting us, and the Torino Scale nicely accounts for both of those.

Pamela: Right, and the thing that anyone that’s gone out and has looked up for any period of time has realized is we’re constantly getting hit with stuff, but the catch is we’re constantly getting hit with stuff that’s of a size that doesn’t matter, so about every 30 seconds a 1 millimeter object hits our atmosphere – shooting star – little, tiny, probably-not-noticed shooting star. About once a year, an object one meter in diameter hits us, burns up, does no damage, and we notice over and over and over in the satellites that are looking for things being blown up — nuclear assessment and things like that — there are dozens to hundreds, depending on how much energy you’re looking at, massive explosions in our atmosphere, Hiroshima-sized explosions in our atmosphere from things that hit us on a regular basis that no one notices because it’s out over the ocean, or over the prairie or something.

Fraser: So, let’s go through the Torino Scale. Let’s start with the bottom, I guess, zero and walk our way up to ten.

Pamela: OK.

Fraser: So what is zero on the Torino Scale?

Pamela: Uh, nice lightshow, maybe — probably not. This is the YU 55, so things that go past that we know exist, they’re not coming anywhere near us, but we can look at them as they go by.

Fraser: So we are certain that they will not do anything to the planet.

Pamela: We are absolutely, positively certain they will do nothing to the planet.

Fraser: OK, so what is a “one” on the Torino Scale?

Pamela: A one is “the chance of collision is extremely unlikely,” about the same as a random object of the same size striking the Earth within the next few decades.

Fraser: In other words, objects are randomly hitting our…what? hitting our atmosphere every few decades anyway, and so there’s just neither much risk, nor much damage if it does.

Pamela: It actually kind of boils down to, “we don’t know much about this object yet. It’s as likely to hit us as anything else, and anything else is probably not going to hit us.”

Fraser: Right. OK. Let’s move on, I want to hear the next one.

Pamela: OK, so this is number two: “events meriting concern,” yellow zone number two. Number two just says “a somewhat close, unusual encounter, collision is very unlikely.”

Fraser: OK. Three?

Pamela: “A close encounter with a 1% or greater chance of collision capable of causing localized destruction.” This is your neighbor’s house is destroyed.

Fraser: Well, it’s more than that, right? It’s like a city.

Pamela: Yeah, but it’s still confined to a region. So we’ve experienced these things in human memory, so it’s…

Fraser: Would that be like Tunguska?

Pamela: Well, Tunguska, yes. It would also be back in 1490, there was a Chinese village that reportedly had about 10,000 people killed.

Fraser: Right, OK. Yeah, and I know we have lots of these iron meteorites that are found in, like, what is it? Campo del Cielo meteorite? And there’s…so like Tunguska. for example. was like a…what? 1908 asteroid, comet, UFO traveling through a wormhole, um…

Pamela: [laughing] Something blew up in the atmosphere and flattened part of Siberia.

Fraser: Right, so in other words, it didn’t cause any damage to Paris or Moscow, but it sure ruined a chunk of the Siberian forest.

Pamela: Right.

Fraser: OK. Alright, so, that is localized damage. Let’s keep going.

Pamela: OK, so now we move out of yellow into threat level orange, and these are threatening events. And I just sound far too mirthful reading these, but destruction is fun! So number five is “a close encounter with a significant threat of a collision capable of causing regional devastation.”

Fraser: Regional…so when they say regional, are they talking about, like, Europe? Great Britain?

Pamela: Yeah, pretty much.

Fraser: Yeah, OK.

Pamela: Let’s just, like, get rid of Australia.

Fraser: So, in other words, if that happens, and great, it hits Australia, then you and me over here in North America would probably be alright.

Pamela: Right, so here we’re not talking enough material getting thrown into the atmosphere that it causes global cooling. We’re not…we have to worry about things like massive fires being caused, but as long as that doesn’t happen, we’re probably good. As long as it’s elsewhere…

Fraser: And that’s only half way up the scale.

Pamela: It’s only half way up the scale, but these are still probable things, so there’s a significant threat, but not a certain threat.

Fraser: Right. OK, keep going up.

Pamela: So threat level six is “a close encounter with a significant threat of a collision capable of causing global catastrophe,” so this is the dinosaurs dying — perhaps.

Fraser: Right, but I think the key there, and this is really weird, right? Because this is essentially complete destruction of the Earth, of all life on Earth, but we’re still…but maybe, right? That’s the trick.

Pamela: It’s the maybe that’s important. It’s the maybe that keeps it from being a red.

Fraser: So maybe the whole Earth will be destroyed, but maybe not. Who can say? Right. OK. Let’s keep going.

Pamela: OK, so threat level seven is “a close encounter with an extremely significant object capable of a collision causing a global catastrophe.”

Fraser: That’s seven?

Pamela: That’s seven.

Fraser: Well, hold on a second, so that is again global catastrophe, and a very high likelihood of a collision?

Pamela: So we went from “significant threat” at six to “extremely significant threat” at seven.

Fraser: Are we going to be destroying the Universe by the end of this scale?

Pamela: We’re just increasing certainty as we go.

Fraser: OK. Alright, it’s just hard to say with these words, you just want, like, is it a 75% chance? Is it a 33% chance?

Pamela: Yeah, they don’t do that for us.

Fraser: OK, let’s go on to level eight. I’m scared now.

Pamela: OK, so we’re now going into threat level red. These are certain collisions.

Fraser: Aaah…certain. 100% chance, yeah… There’s a 100% chance that an asteroid is going to strike. OK.

Pamela: So at threat level eight, we have “a collision capable of causing localized destruction. Such events occur somewhere on Earth between once per 50 years, and once per 1000 years.”

Fraser: So, this would be astronomers detecting a Tunguska-level event, or maybe meteor crater in Arizona, right? And saying…Barringer Crater? Yeah.

Pamela: Beringer.

Fraser: Yeah, Barringer, and saying, “We are absolutely going to get hit by a Barringer. It’s probably going to hit, you know, Paris. Everybody ought to move away from Paris.”

Pamela: See, I’m not actually sure if Barringer is localized or regional because of all of the stuff it tossed into the atmosphere.

Fraser: Right, right, you know maybe that’s just… Yeah, but what is it? A Tunguska happens every 100-1000 years, so it sounds like that’s sort of in the scale.

Pamela: It’s definitely Tunguska.

Fraser: Well, I mean Tunguska flattened a forest for 1000s of kilometers, right? …square kilometers, so it was a pretty big event.

Pamela: Yeah, it was kind of awesome.

Fraser: …dig out a big crater, but that’s kind of what we’re talking about. I can see maybe Barringer being even worse, but the point being…but it’s interesting, you know, the previous level was, you know, “the Earth is completely toast probably,” and now we’re back to “a very small part of the Earth is toast for certain.” OK.

Pamela: Yes. OK, so threat level nine is “a collision capable of causing regional devastation. Such events occur between once per 1000 years and once per 100,000 years.”

Fraser: Ouch. OK.

Pamela: So this is, “We see it coming. Everyone get on a plane and go somewhere else now, please. That part of the planet is about to end.”

Fraser: OK, and number ten…

Pamela: Number ten: “a collision capable of causing a global climatic catastrophe. Such events occur once per 100,000 years or less.”

Fraser: 100,000 years or less?!

Pamela: Yes.

Fraser: So we’re not even talking about like a KT, you know the one that ruined the dinosaurs 65 million years ago; we’re talking about something much less damaging.

Pamela: Well, so this is where you end up with people arguing over what counts as global catastrophe. So, does it count if it changes the weather patterns? Does it count if you have mass extinctions? because we certainly haven’t had a mass extinction in a while. So, people do squabble over those kinds of things.

Fraser: But we are talking about the end of civilization as we know it.

Pamela: Yes.

Fraser: No matter where you live, civilization is going to come to an end.

Pamela: Yes.

Fraser: Wow! So since the Torino Scale has been developed, how bad has it gotten?

Pamela: Well, we made it up to four once, briefly, but the nice thing about the scale is it’s self-correcting as you get more data because up until you get into that red zone, all you’re really talking about is things that might hit the Earth, and how bad it’ll be if they happen to get to “might,” or happen to get past “might.” So Apophis, which we’ve all heard about in the news, is the big one that everyone freaks out about, and we now know it is a zero. There is no chance that we know of that on its next pass past the Earth — and this is all we’re worrying about is the scale’s looking ten years out into the future. It’s not going to hit us then.

Fraser: Although, there’s a possibility of that in 2029, and a completely unknown possibility in 2036.

Pamela: Yeah, so it currently still has, for the 2036 encounter, a rating of a level one because we need to wait and see what happens in 2029 because its orbit will get changed as it goes past the Earth.

Fraser: So the highest…so Apophis, you know, rose in the charts to four.

Pamela: Yes.

Fraser: Which I think they kind of regretted doing that, but…

Pamela: Yeah, well, it was an honest…you see, the problem is that science is something where we’re constantly learning new things, and… It was an honest level four..

Fraser: Yeah. There was enough uncertainty…

Pamela: There was an object in 2006 that temporarily got a level of two, but it got downgraded quickly, so in general, things don’t make it very high on this scale.

Fraser: And they don’t last long on the scale.

Pamela: Right, and what’s kind of amazing is we have all sorts of surveys that are essentially accelerating the rate at which we discover asteroids, so even as we’re discovering more and more and more and more asteroids on a regular basis, we’re not discovering more Earth-destroyers as we go.

Fraser: Right, and in fact, I think, you know, we mentioned this in another show, we’re finding all of big nasties, and have really ruled out a lot of impacts in the foreseeable future.

Pamela: Right.

Fraser: The size of asteroids is the problem that we’re looking for now, and they’re getting smaller and smaller, which is kind of a relief.

Pamela: And the thing interested me, in researching the show, I went through and I looked up historical accounts of people getting clobbered because you’ve probably seen on TV if you’ve ever watched any of the bad science channel specials, the story of the car that got hit, the story of the lady that had one come through her roof, and bounce off her radio and hit her…

Fraser: The dog that got killed…

Pamela: …the dog that got killed, so there’s all these stories that are always in the news. But the thing that got me that I didn’t know about is there’s a number of different (number being 3), number of different areas getting walloped by basically a rain of solar system gravel, and so there’s this story in 1490 that people argue over how accurate the numbers are, but according to the histories, the Chinese province, that I’m about to mispronounce, Chíing-yang, was hit by a whole bunch of asteroid fragments that killed about 10,000 people, and that’s kind of dramatic. And there was a village in Africa that had a rain of fragments, and there’s just all these stories of places basically getting rained on with shards that damage roofs — it’s like a massive hail storm, usually, but that seems to be the more frequent way of individuals having close encounters with asteroids.

Fraser: And so just as we’re recording the show right now, how many objects are on the scale?

Pamela: Well, everything’s on the scale…

Fraser: Oh, sorry.

Pamela: …because everything gets a Torino level.

Fraser: Sure. How many are above one?

Pamela: Well, we have nothing above one.

Fraser: Wow.

Pamela: So there are two objects that we don’t know their orbits well enough to give them a zero, so there’s two things that we’re still following up on that have a rating of one in the near future. So, we’re doing pretty good. With everything we’ve discovered, we are safe for at least ten years, and for the things that we know, with the exception of Apophis, there’s nothing to worry about.

Fraser: Alright. Wait a minute – that was like a nice, pleasant, happy ending to that.

Pamela: That’s why it allows me to giggle while reading the scale.

That

Fraser: That was good. I like you reading the scale. People should…we should have a separate recording of that and then we could just listen to that show – you doing the Torino Scale. Right? Well, that was great. Well, thanks a lot, Pamela.

Pamela: It was my pleasure.

Fraser: And next week, I think, we’re going to actually specifically talk about Tunguska.

Pamela: Yes.

Fraser: And that will be kind of cool. And that was from a listener who suggested that idea for a topic, so we will…we live only to serve, and we will do that episode next, so….

Pamela: And one side comment before we take off: we are recording this as we enter the Holiday season in 2011, and we just posted a bunch of new stuff in our store, including a new t-shirt design for the Venus transit next year.

Fraser: Cool!

Pamela: So if you’re gearing up in your preparations for the Venus transit, and you want a map on a shirt of where the transit is visible, we have that shirt for you. So, go to Astrogear.org and get stuff for the Holidays for the people in your life, and for yourself while you’re there.

Fraser: Sounds good. Alright, well, thanks a lot, Pamela.

Pamela: Sounds great!

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 241: Astrophotography, Part 3: Image Processing

admin — Thu, 01 Dec 2011 20:40:30 +0000

Time for part 3 of our tour through the hobby of astrophotography. You’ve set up your gear, taken some clear images. Now we’re going to help you turn that raw data into the kind of amazing photographs you see in books and on the web.

Show Notes

End of the World (NOT) Cruise
Google+: Fraser, Pamela
Subaru Telescope
How to Create a Flat Field — AstroWise
IRIS software
REGIM Software
A list of software for Astrophotography — AstroPix
Maxim DSLR — Michael Covington
GIMP
Adobe Photoshop Lightroom
RegiStax
FITS Image Viewer
IRAF Software
AIP4WIN Info and Handbook
CCDSoft
Maxim DL – Oceanside Photo and Telescope
Mira software
IDL software
FITS Liberator
Cloudy Nights Forum
Universe Today Flickr Group
The World at Night (TWAN)
Ice in Space
Astronometry.net — for automatic image annotation
Astrodatamining.net – another resource for annotating objects
http://iraf.noao.edu/ – for filtering the sodium light and increase the contrast

Transcript: Astrophotography, Part 3: Image Processing

Ep. 240: Astrophotography, Part 2: Techniques

Fraser: Welcome to AstronomyCast, our weekly facts-based journey through the Cosmos, where we help you to understand not only what we know, but how we know what we know. My name is Fraser Cain; I’m the publisher of Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University – Edwardsville. Hi, Pamela. How are you doing?

Pamela: I’m doing well. How are you doing?

Fraser: Doing good. So, we should plug again about the “End of the World” cruise. Just to let people know, we are kind of quietly plugging the “End of the World” here at AstronomyCast before we plug it in sort of wider audiences, so I haven’t mentioned it on Universe Today, and we haven’t got Phil over at Bad Astronomy to mention it and so on, mostly just…not that he necessarily would, but we’ll ask, but just cause we want to give AstronomyCast listeners sort of a more of a chance to get in. And if you do want to participate, book a room on the cruise, book a cabin and join us. So remember we’re going to celebrate the end of the world, December 21, 2012, cruising the eastern Caribbean on…you know, and even visiting Mayan ruins when it’s all supposed to end.

Pamela: So you can get all the details if you go to Astrosphere.org and we have a phone number for you to call. The travel agent who’s booking everything, her name is Zelda, and when you talk to her just tell her, “AstronomyCast sent me,” and we’ll go on our own adventure thanks to Zelda.

Fraser: Perfect. Alright, well let’s get on then. OK, time for part three of our tour through the hobby of astrophotography. You set up your gear, take some clear images, and now we’re going to help you turn that raw data into the kind of amazing photographs you see in books and on the web. So would it be safe to say that a lot of the magic of good astrophotography comes from this post-processing world? Software…?

Pamela: I’d say the vast majority of the magic comes from the post-processing.

Fraser: Yeah, yeah, that it’s really…I mean, you set up your, you’ve got good gear, you set up your camera, you press a button a bunch of times, but there’s actually so many options in the way you set up your software, and the way you set up your image, and the way you combine them and collect them and tune and remove noise and all that. That’s where it really comes together.

Pamela: Well, what’s really amazing is you can take the best images any human being on the planet has ever taken, and if you process them wrong, it will be useless junk, but you can take some kind-of-mediocre images on the sky — clouds, Moon pollution, whatever it is that affects the images, but with proper post-production, you can make those images really shine.

Fraser: Right, and so then what we’re really talking about today is, you know, you’ve taken all those pictures, you’ve got them filled up in your camera, you connect them to your computer, you download all of those raw images, and then what on Earth do you do with them to then make that final photograph? So, I think, let’s go back again and let’s talk about the different, you know, the different styles of astrophotography, the three styles that we’ve already talked about, the connecting your digital single-lens reflex camera to a tripod, taking some long…a series of long exposures in raw format, you know, and they’re going to be seen on the camera, you need to pull them off on your computer. We’ll talk about the process where you’ve got a webcam attached to your, you know, medium-range telescope, and you’re trying to go after the planetary stuff, the bright objects in the sky, then the really detailed, $20,000 camera-telescope-mount set-up, where you’re using a CCD array to pull data off as well. So let’s go back to the DSLR route. Let’s…you know, we talked about last time that we want to get these really, nice RAW images, the RAW format: R-A-W, you know, like all in capitals. What do I do with them? And I’ve…you know, what now?

Pamela: Well, so the first thing you do, no matter what, is you back-up your data, and the reason I say this is when you’re going through processing the images, it’s very, very easy to click a switch in your software such that it overwrites the original images, and if you don’t like what you did, you can’t go back and try something else if you overwrote them.

Fraser: Right, and that’s where the art comes into this is, as long as you keep that raw data separate, take a shot at it try to get an image result, and if you don’t like it, just go back to the beginning, take another path, take another crack at it, and maybe you’ll get an outcome that you’re a lot happier with.

Pamela: And this is something that even the pros do. I’ve been working with an absolutely amazing telescope driver image-reducer, basically, data miracle man out at Southwest Research Institute, and he’s trying to coax amazing images out of the Subaru Telescope, which is one of the world’s largest telescopes down in Hawaii. And he’s on his third pass through the data, each time revising the software he uses, each time changing the options that he takes to get it just a little bit better, and a little bit better, so no matter how good you are, there’s always that chance you’re going to start from the beginning.

Fraser: Now with the, sort of, that original method we’re talking about, the first of our three techniques, you know, I’ve got all these raw images of, like, wide-field, Milky Way, you know, each one was for, whatever, 10-30 seconds…what do I do with them?

Pamela: So the first thing you do is you need to do some calibrations. So here is some steps where, first things first, you can do a number of different ways to check for variations in how sensitive your camera is across the entire field. You can either take images of an evenly illuminated surface: a white wall, the twilight sky. Some people actually will create out of plexiglass these light boxes that they then attach their camera to out of focus to get this evenly illuminated image. Once you have these evenly illuminated images — these are called flat fields. The other type of thing that you want to do is measure all of the noise within your detector. So you can do this using what’s called dark images. This is where, depending on your camera, either your camera automatically every time you take a long exposure takes a second long exposure with the shutter closed, and then it subtracts off that shutter closed image because that image only contains the noise, and if the noise is consistent from one image to the next, when you subtract it off, you can just get rid of that noise. This is the same way noise-canceling headphones work, but this is the light equivalent of those noise-canceling headphones.

Fraser: And is this ability somehow provided by software like Photoshop, or is there some kind of special software that you need to use?

Pamela: Well, you can do it in Photoshop, but Photoshop’s not designed for it, so here you want to break down and either download some software – there’s a number of options out there, IRIS is a good one that runs multi-platform, there’s another one called REGIM – it has a lot of its instructions in German, so I tend to go to the IRIS site instead. A lot of that website is written in French, but the IRIS stuff itself is in English. These free software packages will help you figure out how to do all this image calibration. Now, if you’re interested in spending some money, Maxim DL has Maxim DSLR as one of its options, and this is an amateur astronomy imagery production package that has been tailored to meet the needs of everyday people trying to get the best astronomical images in the world. There’s lots of other software out there; these are the ones I find useful for working with DSLR cameras.

Fraser: And so, what do they do to your images? I mean, do they output a whole bunch of more images, which then had their light balanced out, or does it actually handle the merging as well?

Pamela: It does all of these different steps. So the first thing it will do is if your camera doesn’t automatically remove the dark current for you (which a lot of the cameras do), you feed it, you tell it what are your dark current images, and it will combine all of them and then subtract those off of your science images, your flat-field images. Then the next thing it will do is you feed it those images that I told you about of the evenly illuminated surface. So you feed it those, it adds them all together, but it does it in a way that averages everything together, so if one pixel is hot in only one image, it ignores it, but if it’s always a little bit hot, it averages those values together to get it hot, but in a typical behavior, so now you have a typical, how-your-camera’s-misbehaving image, and this it divides off so that anywhere where your camera’s a little too sensitive to light, it makes it fainter, anywhere your camera’s typically under-sensitive to light, it makes it brighter. And this flattens out your image so that the sky is evenly illuminated, if it’s actually evenly illuminated. If there’s dust, it fixes the dust. So that’s the second step.

Fraser: So is that just like a one-stop shop? In other words, you’ve got your RAW images, you feed them into one of these software packages that we talked about, IRIS or Maxim, and then out comes one of your final ones? After you’ve mucked with all the features and you tweak all the settings, and you color balance and blah, blah, blah, you know, read the instruction manual, the point being (that was the technical term, of course)… bayesian light, annotation, heurism, um, but you know, [laughing] you, you…will that just output your final picture, you know? You’ll be mucking with the features and then out will come the final image, or do you gotta do more?

Pamela: No. So you use the software like REGIM, like IRIS, like Maxim DSLR to get all of the noise that you can get removed from your images, to get all of the dust and the optical issues. You use it to fix all the stuff that’s wrong, but you still have images that aren’t art. You still often have just black and white images. To go that extra step to stretch the colors, to adjust what do you actually want red to be — here most people actually resort to Photoshop, and that’s where the big bucks are. Now, if you’re not ready to spend the money in Photoshop, a much harder to use, but also a very powerful software tool is GIMP. GIMP is the open source community’s answer to Photoshop. It has lots of powerful tools, it has fairly good documentation, it’s not as intuitive to use as Photoshop, but it’ll get the job done.

Fraser: Yeah, now Photoshop is not intuitive to use, so that’s…unfortunately, it’s about three steps below the controls of a 747, but you know, I mean, I use Pixelmator on my Mac and it’s good. It does most of the things that Photoshop does. Gimp is free if you’re willing to sort of beat your head with a hammer, and Photoshop is expensive. And someone in the Google plus hang-out is recommending Adobe Lightroom, so there’s another choice as well, but the point being that that’s where the art happens. You’ve got that final place where you then create the art. You know, I can see situations where you’ve taken this great big wide-field image, you’ve got some horizons, some trees, and then you’ve also got the night sky up above and you’re trying to make it look that you can see the you know that horizon and see the city lights, but then at the same time have the Milky Way stretched above and it all look like art, so I think that’s really cool. OK, now let’s kind of go back around to that next technique that we’ve talked about where we’ve got the little webcam, we’ve connected it to our eyepiece and we are dropping out video of Jupiter, or Saturn, or you know, of the Moon. What, uh, how does that work then?

Pamela: Here it’s actually awesomely easy thanks to a piece of software called RegiStax. Now, it’s only going to be easy if you have access to a Windows system. So all you folks like me out there who are running OSX, it’s time to install the MWare BootCamp parallels; all you people on Linux, it’s time to dual boot. Suck it up, pay the money for windows because RegiStax is free. It doesn’t balance out in the end, but RegiStax, if you’re going to be doing this sort of astro-webcam imaging — it’s designed for planets, and planets are actually much harder to cope with than stars because when you’re trying to align all of these images, if you’re looking at a star field, you grab 5, 10, 20, 30 stars – as many stars as you can, and you tell your software, “Grab those stars in every single image. Align, stretch, rotate, whatever it takes to get those images to line up perfectly.” Do not try this at home in Photoshop; you will hate yourself. Use astrophotography software to do the stacking. Now, with planets you often just have one giant, round (hopefully round), object that doesn’t have sharp features to align on. RegiStax has coded black magic in it where it’s able to figure out, based on the edges of the sphere, what needs to be done — sphere projected into a circle for your image, what needs to be done to align everything. And it’s also pretty good about helping you reject things because there’s always going to be those images where the sky misbehaved, where you walked too hard and you jiggled your telescope, and it will help you go through and do everything you need to do to get a great image out the other end.

Fraser: So this software will line up all the frames to help make sure that you’ve got everything nicely lined up, and then let you go through the frames and just kind of go, “Ah, blurry — throw it out. Oh, that’s crisp — let’s keep that one. Ooh, there’s a little bit of a better edge on the storm there — I’ll keep that one.” And then, I’m guessing, give you some way to sort of pull out certain features and push other features back a bit.

Pamela: Well, what it’s going to allow you to do is add everything together, and it’s in this adding together part that it takes the information, and anything that’s faint when you add it together is going to get brighter and brighter and brighter. Now, this isn’t going to allow you to say, “I want the red redder.” Again, you use RegiStax to do the crunching part, and then you dump the result in Photoshop or Gimp.

Fraser: Right, but you’re going to end up with one image — one great, big, you know, high-definition image that you’re then going to color balance and change the saturation and the hues and all that kind of stuff in Photoshop, but you’re no longer going to have access to the raw frames unless maybe you somehow dumped them out into layers in Photoshop.

Pamela: That would be painstaking and awful, and don’t do that.

Fraser: That’s where you’re saying, “Don’t do that.” OK, OK, great… [laughing] and one of the users in the Google plus hang-out says that RegiStax is awesome, but as user-friendly as an angry porcupine, so you’ve been warned that it’s as user-friendly as an angry porcupine.

Pamela: And a lot of this software is as user-friendly as an angry porcupine. Occasionally, it’s as user-friendly as an angry hedgehog.

Fraser: Right. Like adorable, but still prickly. Um, yeah, yeah, well I mean, in a lot of the cases it’s made by programmers, by astrophotographers, attempting to roll their own solution and then they get to the point where, “Well, it worked for me, but I guess it would work for other people as well. Sure, I can share it with you,” and then somehow it turns into a product at some point, and you know how it goes.

Pamela: Photoshop is THE easiest to use of all these pieces of software.

Fraser: Photoshop is awful! So, that’s terrible; that’s not saying a lot. OK, well then let’s move on to that third methodology because I think that is the one that’s the most complicated, I think, in my mind.

Pamela: And this is the time that you separate the apprentices from the master sorcerers. When you have your FITS images coming off of a CCD…

Fraser: FITS images? What? What? Wha?

Pamela: So with your regular DSLR camera, you can get RAW, you can get TIFF, you can get jpegs. When you move on to using CCD cameras, it moves to an international image standard that works with all sorts of neat, nifty arrays and metadata, and it’s a great image standard that takes up lots of disk space, and it’s the standard we use for astronomy. It’s called FITS.

Fraser: FITS, OK…jpg, gif, FITS, sure. OK.

Pamela: And so once you have your FITS images, you have to do all of the nastiness that you had to do with your DSLR cameras, so your subtracting off your dark images, here we also have bias frames, so you’re subtracting off your bias frames, you’re creating your flat fields, you’re dividing off your flat fields. You are then image aligning everything, and to do all of this for free, you want to use software called IRAF that will make you cry. It’s pretty much a guarantee [laughing]. I’ve been teaching for Swinburne Astronomy Online for a number of years and once or twice a year, I have a student take on IRAF and I’d say that majority of them have either wanted to act violence upon their computer, or they’ve simply ended up weeping at their keyboard [laughing]. And the thing is, though, once you make it past the tears and the anger, and the denial, and you move on to acceptance, IRAF can do absolutely anything and it is completely free. It’s powerful — it just does miracles to bad images. Now, to those of you who’d like something a bit friendlier, we’re now back to the angry porcupine, or the angry hedgehog level of software. There’s a number of pieces of software out there. Maxim DL, which is the same company that does Maxim DSLR, they’re actually different versions of the same piece of software. There’s AIP4WIN, which has the best user manual out there. You can buy the user manual by itself, and it’s kind of the go-to manual in how to reduce amateur astronomy CCD data. There’s CCDSoft, there’s other kind of in-between educational professional and amateur software, there’s…Mira is a piece of software that’s out there, and for those of you who want to spend the big bucks, there’s software called IDL, which is kind of it’s own image language, so when you see these amazing color simulations of, like, asteroids hitting the ocean — that simulation was probably written in IDL, and you can also use IDL to reduce all of your astronomy data.

Fraser: Right, and so then we’re going to have…now is the CCD connected to the computer, is it going to be this again, dropping these great big images in FITS, these FITS graphics? And then you’re going to then import them in, and the software in, you know, is going to, you know, you’re going to be doing the settings, and setting: this is the dark removal, and that’s the this, and that’s the that, and you’re going to use all the settings depending on whether you’re trying to make a pretty picture, whether you’re trying to do science and come out with this, again, you’re going to come out with a final raw image, or are you going to come out with multiple images, which you’re then going to combine in Photoshop? What next?

Pamela: So CCD, if you’re using a highly-sensitive black and white CCD, looking through filters, which is what I’d recommend, you’re going to end up with an absolutely through-the-R filter, amazing combined image, an absolutely amazing, through the V or the G, something that gives you green colors image, or whatever set of colors you’re using. You’re going to get each of these different black and white images still in FITS format, and then there’s that little piece of software called FITS Liberator that’s available completely for free from the Hubble Space Telescope Science Institute. It’s actually put together by the European space agency, and this free piece of software is going to allow to take that FITS image and play with it until you get the stretch exactly the way you want it, until you get the white balance exactly the way you want it, and then it outputs it to something that you can use in Photoshop or Gimp. So we’re back to Photoshop and Gimp again.

Fraser: Photoshop and Gimp, right. And you’re going to import them in as one image or are you going to put them as three images, and then set one for your red, and one for your green and one for your blue, and then mess with it that way?

Pamela: Right. That’s exactly what you do. You import them in as individual images and then you copy them in to your different image channels. And one of the neat things about Photoshop is you can actually play with it such that we talked about while you’re taking images that you should take some unfiltered images that you use as illumination images. These simply allow you to sharpen things up in the end, so you can use that to mask the entire image using either a darkened or a lightened layering effect. You can then take and make your red channel some combination of images through a red filter and an H-Alpha filter, some combination of H-Alpha and IR, so you can combine five, six different filters into those three-color channels that we use for RGB in all sorts of creative ways that allow you to get these amazing images.

Fraser: That is really cool. That’s…and again, it’s the most complicated way, but again, it’s the way that gives you the most control at every step of the process, allows you to both do science and make pretty pictures if you want, and the final results are worth the effort, so I think that’s fantastic. Well, I think we’ve come to the end of our three-part trilogy on astrophotography, and I think we pulled it off. I think…

Pamela: I think we did.

Fraser: Yeah, I mean, talking about astrophotography… Seriously, we have had this show in the works for like 100 episodes, we’re like, “Yeah, we should do…we’re going to have to talk about it…how’s that going to work?” So anyway, I think that was great. I think, someone can have this on while they’re in front of the internet and be browsing for all these different pieces of software and pieces of gear, and take a look at it and check through our show notes. We’ll have links to lots of stuff, so I think that was great.

Pamela: And we’re sorry if we were a terrible influence on you, but I know this three-part series led to me buying a new Canon Rebel T3I camera, so I can go out and play along with our show. And for those of you who want to learn more and want to find a community of people doing this, the Cloudy Nights forums is a great collection of human beings who know their hardware, so…

Fraser: Well, I’m going to sort of shamelessly self-promote as well, which is that we post amateur astrophotographers on Universe Today almost every day, sometimes two a day, and we’re always hungry for people to send us the images. So if this has in any way gotten you inspired you to take some pictures, you know… We’ve highlighted everything from people showing conjunctions, and pictures of the Moon, they’ve just…or like a really nicely-framed image to the really high-end CCD stuff, so you know, if you want an outlet to do that, we’ve also got a Flicker group on just for Universe Today’s astrophotography. And if you come to Universe Today and look at any of the astrophotography photos that we post, you’ll see a link to that Flicker group, then all you’ll need to do is just post photos into that Flicker group, and then we will pluck them out and highlight them in Universe Today, so not only are we going to get you hooked on this hobby, but I’m also happy to promote you and get your name out there, so you know — get started!

Pamela: And Fraser’s not the only one doing this really well.

Fraser: Yeah, I am. It’s just me; it’s the only place. No, no, there’s lots of good stuff.

Pamela: The one other place that is my favorite random historical sites images to use for PowerPoint presentations is there’s a site called The World at Night – TWAN, and they have all of these amazing images of cities, of old architectural ruins, of those geologic features that appear in every geology book, so you have Ayers Rock in Australia, for example, so you get this combination of amazing things on the planet Earth, and amazing things in the skies above, so…

Fraser: Perfect.

Pamela: Lots of communities to join into…

Fraser: There’s tons, there’s Ice Hunters, which is Mike Salway’s community…yeah, there’s a ton. Even Flicker is great, Picasa, even on Youtube there’s some great stuff, so there’s lots of places to go.

Pamela: And Astronomy.net will put all of the metadata on your image, so that other people looking at your image know, “Oh, that’s this place on the sky,” so that’s a project by David Hogg, and they have plug-ins that work with Flicker.

Fraser: Sweet. OK, cool, well thanks a lot, Pamela.

Pamela: My pleasure.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 240: Astrophotography, Part 2: Techniques

admin — Mon, 28 Nov 2011 23:15:02 +0000

In the first episode, we talked about the gear you’ll need for your expensive astrophotography hobby. This week we continue our discussion, and talk about the techniques you’ll use to get those amazing photographs. Bring a hot drink, and get ready for some cold nights. But trust us, it’ll all be worth it.

Show Notes

Astrogear
Google+ — Pamela, Fraser
McDonald Observatory
Raw format and why — Northlight Images
Night Sky Photo Tips – Dennis Mammana
More tips from the One-Minute Astronomer
Astrophotography Hints and Tips — EAAS
How Image Stacking Works — Keith Wiley
Webcam Astrophotography Tutorial for Planets — Ray Shore
Using ToUCams for Astrophotography
Cloudy Nights (Telescope reviews, astrophotography forum)
Ice In Space Forum
Filters for Astrophotography – Astropix
Info about Hydrogen-Alpha
Avoiding “square” stars (discussed in this astrophotography equipment primer by Starry Wonders)
John Chumack
Tom Davis
True or False (Color): The Art of Extraterrestrial Photography – Universe Today

Transcript: Astrophotography, Part 2: Techniques

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Doing really well, too. So you wanted to plug something…

Pamela: I did. It’s the Holiday season. We are recording on Thanksgiving Eve, and I know many of you are gearing up to give gifts, and if you have a kid, a comic book lover, or actually just about anyone in your life, we have roughly 1000 Hanny and the Mystery of the Voorwerp comic books, and we‘d love it if you purchased 1 to 200, so go to Astrogear.com, and we’re also going to be posting up new t-shirts and all sorts of stuff up there, so consider AstronomyCast as you’re doing your Holiday shopping.

Fraser: And the second thing is we are once again recording this episode of AstronomyCast as a Google plus hang-out, so once again, we have eight of our closest friends listening in to the episode, and correcting us as we make mistakes, and suggesting ideas that we hadn’t…hadn’t even occurred to us as we are doing the recording, so thank you to everyone who is with us today, and you get to see the way the show really gets done. But if you want to do…participate in joining us in the future, all you have to do is circle either me or Pamela in Google plus. Google plus is free to join, you don’t need an invitation, and then you can circle us, and then you’ll see the announcements when we’re about to do the episodes, and then you can join our hang-out and watch the show, and then hang out for, you know, usually half an hour afterward and we answer questions and talk about Space, or Thanksgiving, or whatever, so alright…Cool! Alright, well let’s get on with it then. So in the first episode, we talked about the gear you’ll need for your expensive astrophotography hobby. This week we continue our discussion and talk about the techniques you’ll use to get those amazing photographs. Bring a hot drink and get ready for some cold nights, but trust us, it will all be worth it. So Pamela, before we get into this, do you have an anecdote of, like, just some brutal astrophotography observing work that you’ve done?

Pamela: Well, so I study variable stars, and I got to use the 30-inch at McDonald Observatory when I was a graduate student and it has a 1-degree field, which meant that not only did I get the variable stars I was looking at, but I got everything in the field around it. And the awesome thing about doing variable stars is you take image after image after image after image, which is exactly what you do when you want to get high-quality astrophotography images, so I spent lots of nights out there, and was able to build some pretty awesome images, but one of the things was is you get into a rut occasionally, you’re sitting there, you’re at your computer, you’re taking image after image after image, and I was doing 600-second exposures and there was one point, I’m sitting there and the old man on the mountain, the engineer who babysat us made sure we didn’t destroy the telescopes or anything, came into the observing room I was sitting in, and he was just like, “What are you doing?” in the standard, you-stupid-graduate-student tone of voice. I’m like, “I’m taking images.” And just as he says that, an image comes onto my screen that’s completely starless. I am looking at absolutely nothing, and I look at him and he looks at me, and he just uses his hand to beckon me outside and I get outside and the entire dome is just like underneath this thick wall of clouds that came out of nowhere as near as I’m concerned, so it’s amazing how the sky can change in 600 seconds, and I felt rather foolish at that moment in time.

Fraser: So, right. So if you’d practiced some better technique, perhaps you would have noticed the fact that you were getting clouded out. And so last week, we talked about sort of the three main ways that you can do astrophotography. One is you take a really nice, you know, digital SLR camera, connect it onto a tripod and just do some really nice long exposure images. Ideally, track with the motion of the sky, and, you know, get those beautiful Milky Way images and star fields and things like that. The second way is you take your webcam, hook it up to the eyepiece of your sort of medium-level grade telescope, and get those amazing images of the planets and the Moon and things like that. And the third way is the, you know, the price of an SUV, where you hook up the CCD camera to your $20,000 Ritchey–Chrétien telescope and, you know, take some amazing Hubble-style deep sky photography. So then let’s go back and run through those different methods and talk about what are the kinds of techniques that astrophotographers use to get those kinds of images. And I guess, you know, we should probably start with the images, you know, the sort of long-field stuff or the long-duration, long with the DSLR camera. What’s your method to get the raw images?

Pamela: Well, the first thing you need is some sort of a camera that allows you to output in raw format, so that sounds kind of like, “Oh, of course it’ll happen!” but when you’re purchasing your DSLR camera, take that into consideration, and then remember to switch the setting.

Fraser: So, hold on a second here. You talk about raw format, and like I know that my Canon T3 will…I can take jpegs and I can take this raw format, and so I want to shoot with that raw format and that creates these monster digital files, right?

Pamela: Right, so what’s happening is when you use jpeg images, it does some sort of a compression. And basically what it’s doing is it’s saying, “OK, this set of pixels over here – they’re all the same color, so I’m going to store them together. This set of pixels over here – they’re all the same color; I’m going to store them together,” but when you store in raw format it actually stores the data for every single pixel separately, so it takes up a lot more space. It’s the difference between saying, “pixels 1, 10 – 20, 100 are all black, and saying 1, 1 black, 1, 2 black, 1, 3 black.”

Fraser: Right, so there’s a like a compression and loss of data.

Pamela: Right, so with raw you have none of that loss of data, and it allows you to keep all the information for every pixel — and you really need that for astrophotography.

Fraser: OK, but those files are BIG.

Pamela: They’re HUGE, but it’s worth it in the end. If you’re trying to get the best image you can, why start out by throwing away data as you’re taking your image?

Fraser: OK, so you’ve set these big, long exposure times, and how do you go through that process? How do you gather that much light?

Pamela: So there’s two different things that you need to consider: one is how long are you going to keep your shutter open, and the other one is how open are you going to make your aperture. Now, the two of them actually go together. If you’re going to try to take a short exposure of the night sky, open that aperture all the way out. If, on the other hand, you’re looking to take a five-minute or ten-minute exposure, you might want to close your aperture down just a little bit as you’re taking that full-sky image, so that light pollution, moonlight, um, all of these different factors don’t cause the sky brightness to look so bright that it suddenly appears like you’re taking a twilight image. As you take these long exposures, it’s amazing how much sky brightness you pick up. So one thing that you actually want to do is you want to play, to experiment. You want to try that 300-second exposure with the aperture one click closed, that 300-second exposure with it two clicks closed, and you really don’t want to go longer than 300 seconds, and you probably don’t want to go longer than 30 seconds unless it’s an ice-cold night and you’re far away from granite and no supernova has gone off recently. And the reason I say that is if it’s a warm night, then you’re going to run into problems with the heat of your electronics bringing up the background noise in your images as you take longer and longer exposures, and if you’re either in a very granite-rich area or there’s some other reason – a solar storm or something else that’s causing a lot of cosmic rays, those will cause all of these little, bright pixels in the background that are a pain to correct for, so by having reasonably short exposures, you don’t get as many cosmic rays per image, and you don’t…

Fraser: Are you kidding me? Is this like a joke?

Pamela: No, I’m not! This is a real concern.

Fraser: You’re actually telling me that I have to be concerned that cosmic rays and radiation from granite is going to put noise into my beautiful astrophoto?

Pamela: This is an honest-to-God problem.

Fraser: Really?!

Pamela: This is one of those things that drove me crazy as a graduate student because a single cosmic ray hitting a star blasts that star out of usability, so you’ve only wrecked one pixel, but that one pixel exploded that star’s values. Now, you can also get these glancing blow cosmic rays that cause stripes of bad pixels, and all these other annoying things, so yeah, you have to actually start worrying about cosmic rays, and the longer your exposure is, the more cosmic rays your exposure is going to have.

Fraser: If you say so…well, that sounds pretty weird to me. But, right, but what you’re saying then is it’s this balance between aperture and exposure, that you open up the aperture to pull in more light, and you don’t have to necessarily do as long of an exposure, or you can shut down the aperture and do a longer exposure, and there’s not going to be any one way that’s going to make the best picture. As you say, it’s about playing. It’s about trying one idea, trying a different idea, and see what works best for your sky, your technique. You know, if you set the exposure too long, it might blow out the Moon. If you don’t do it long enough, the stars are going to be too dim, so it’s just a matter of finding that happy medium.

Pamela: And there’s no one right answer because the Moon keeps changing in phase, everyone has a different characteristic to the light pollution — one night your neighbor has the light on, the next night they don’t – all of these things add up to chaos, but as you get practiced, you can look at the sky and say, “Ah, tonight I need to…” and you can do what you need to do. It’s like learning to play violin. You instinctually learn where your fingers go every time, and you can make adjustments for temperature and other things through tuning that you know how to do instinctually.

Fraser: Right, right…OK, cool. And so, you know, we talked about the gear, but essentially you will be messing with your aperture and your exposure length, which, you know, every camera is different where the setting is on that, and you will be recording your photographs as raw images and then attempting to dump these into your, you know, some way of…your repository, and you’re going to be processing it — and that’s a future show, that’s episode 3 if we’re going to talk about the processing methodology, but really it’s just about… I mean is there anything else sort of technique-wise except you go out, you set up your camera, figure out your happy place with your exposure and your aperture, and record those raw images?

Pamela: Well, I think the one thing you have to remember to take into consideration is it’s not one perfect picture you’re trying to take digitally because you can add things together. What you’re trying to do is get a series of images that aren’t overexposed, a series of images that have that black sky and are still showing the stars, and then you stack those images together, and by adding them up, well, you don’t have that many cosmic rays to worry about, comparatively, because you can take…one nice thing is you add them up and say, “Ah, there’s a cosmic ray in only one of these ten images,” and you can correct for it. If you only have one really long image, you can’t correct for it. So you’re going to add these images together, and it’s as you add them together later in that next show we’re going to have that you end up finding all of the nebula, you end up finding all of the faint galaxies. So your goal taking your picture is to keep your black sky and get as much light as you can while still having your black sky.

Fraser: And so even with those wide-field, you know, those beautiful images you see of the Milky Way rising up over some desert sky, you know, those are done with a series of shorter exposures that are then stacked?

Pamela: Yes.

Fraser: Or are they done with one big long exposure? So you wouldn’t do a big, long like minutes-long, hour-long exposure. You would take a series of shorter exposures in a raw format and then stack them on computer.

Pamela: Exactly. And the other thing about images like that is you’re worried about, well, the sky is rotating, and you can have your telescope set up perfectly, but no matter how perfectly it is, something is going to cause the tracking to not be absolutely perfect. Every telescope in the world there’s something that is correcting that tracking, and unless you have some sort of an auto-guide system, you’re going to slowly, over time have your stars drift, and by keeping your exposure shorter, you don’t end up picking up that drift.

Fraser: But even if you have some kind of tracking, like, if you’ve got your, you know, you’ve got it connected on an equatorial mount, your connecting with the sky, that’s still not the way to do it. The way to do it is to…

Pamela: It’s still not good enough.

Fraser: It’s not good enough.

Pamela: Over the course of minutes – and you’re going to be taking exposure after exposure adding up to minutes – it’s going to move one or two pixels, and that one or two pixels blurs your image.

Fraser: Makes it all blurry…yeah, OK, so we’re taking…so we’re going to capture, you know, even if we’re tracking, we’re going to capture a little piece of sky, and then we’re going save that file, and then…and our camera might be tracking the whole time, where we take a little picture, take another little picture, and just build up that, OK that’s perfect. OK, let’s talk about that second method then. We talked about the…where you’re taking the planetary astrophotography, where you’ve got your mid-range telescope, and you’ve connected your eyepiece, you’ve connected a cheapo webcam up to your eyepiece, and you’re then capturing image after image after image. So what’s the process there?

Pamela: So here it’s often a matter of getting rid of as much light as possible. This sounds really strange, but when you’re looking at Jupiter, when you’re looking at Saturn, you’re looking at something that’s going to saturate your detector, and so sometimes you end up having to do crazy things like putting a cardboard cut-out on the front of your telescope. So, what you want is to have in every single frame a not-fully-saturated Jupiter. Ideally, you want to know at what point does your detector stop catching light. So there’s usually numerical values associated with every pixel. The CCDs I’ve used have usually gone from zero, which is absolutely nothing, to around 5,000 counts, they really stopped functioning, and so you need to figure out what’s that count at which it stops functioning and come about a third below that is where you want your maximum pixels to go. That way you can get a full dynamic range, you don’t have to worry about blowing out your detector, and there’s other things like where is your detector linear? Now, for pretty pictures you don’t have to worry about that as much, but the idea is…ideally, you double the number of photons that hits a pixel and you double the brightness. Well, at a certain point, that pixel starts to fill up and you just can’t add enough more photons to it to double how much it’s detecting, and it loses sensitivity that… there’s a whole bunch of other stuff, and I’d start to have getting into quantum efficiencies and that’s beyond us right now.

Fraser: No, I’d like to go into that…but no, no, but I guess the part that I don’t really follow then is, I mean, you’re taking your webcam, and you’re putting it onto your eyepiece and then you’re just letting it run, right? You’re just recording like the highest quality video that you can get, and then you’re putting stuff in front of your screen, you know, some kind of cardboard cut-out in front of your screen, you’re turning up and down the color balance, the “gain” of the camera itself to get that perfect happy medium, but then how long are you just letting it collect for?

Pamela: As long as you can.

Fraser: Like, hours?

Pamela: Sometimes, it depends on what you’re trying to do. So, I’ve seen amazing videos that are taken where…so with Jupiter, the planet’s kind of rotating, and if you go for hours, you can build up movies of the rotation of Jupiter, but if you just want a stunningly beautiful picture of Jupiter, there you just want to go a couple of minutes, and if you’re taking several frames a second, a couple of minutes is going to give you more images than you know what to do with because the catch for using a webcam is after you’re done capturing this video, you’re going to go through it frame by frame by frame looking for the sharpest images, and you’re going to throw out the ones that aren’t sharp.

Fraser: Right. And that’s again talking about technique, but yeah.

Pamela: So, here as you take your images, pick a nice beautiful night, get everything so that you’re not saturating your images, and take a few minutes of frames on Jupiter, if you want to do that entire movie of its rotation, take a couple of hours, but if you just want a pretty picture, you’re just looking at a couple of minutes of video.

Fraser: Right, so you’re going to take a couple of minutes, you’re then going to, yeah, you’re then going to go through them frame by frame, so a couple of minutes is probably enough time because if you go longer than that in the case of, say, Jupiter, the object is going to have rotated and then that’s going to introduce blur and more problems into it as well. So it’s more about getting a whole pile of good frames you can then stack later. OK. Awesome.

Pamela: And this works for Mars, less blocking of the front of your telescope required, and Mars is particularly tricky because it’s very tiny, so you want to push what your telescope’s capable of doing. So this is where you want to get as much magnification as your telescope can support and as short an exposure as you can possibly get on your video camera. So wait until Mars is at its closest point to the Earth; wait until it’s at opposition, and give it a try and you’d be surprised what you can get. Looking at it with your eye, your eye doesn’t have the time resolution your video camera has, so you can get a sharper image with your video camera and then add all of those frames together and you can actually make out the icecaps, you can actually make out the volcanoes and the valleys. It’s really quite amazing what you can do.

Fraser: Now, are you recording it in any special way, or are you just recording it straight in whatever color sensitivity your webcam wants to do? Like, do you need do it in black and white, or…?

Pamela: So, what I’d recommend is actually getting a black and white, low-light security camera or getting one of the two-cans, two-cams rather. The two-cams are the ones that are preferred by most astrophotographers, and I believe that those come in both black and white and color, and just follow the user’s manual for your particular camera. One of the things that we run into as a problem with this show is technology is constantly changing, so I’m trying to talk generically, but where the technology’s constantly changing, do what’s recommended for your particular camera. Avoid compression as much as possible, and try and save things in as raw a format as you can.

Fraser: Right, so you’re going to get…whenever you’re listening to the episode of this show, go and lurk around the astrophotography forums and find out what webcam people are currently recommending.

Pamela: Cloudy Nights is an awesome place to go talk to people.

Fraser: Yeah, and/or IceHunters, which is Mike Salway’s forum. Yeah, so that’s to get that latest gear. We try to be timeless with this episode. Now, what about filters? We didn’t talk about filters with the taking night sky, wide-angle stuff because you’re just going to be using your camera with its different lenses, but are you going to want to use any kind of filter when you’re doing the planetary stuff?

Pamela: When you start getting into been-there-done-that-let’s-see-what-I-can-do-that’s-the-next-step-up, that next step up in webcam work is where you start buying the filters. You can get filters that can accentuate the icecaps on Mars, that can accentuate the banding on Jupiter, but the place that filters really start to change your perspective on the sky is when you go that next level, to the “SUV’s worth” of equipment, when you have that full CCD detector and when you have that either Schmidt Cass or Magneto Cass or Ritchey–Chrétien telescope.

Fraser: I know the filters are really important for the deep sky stuff with the CCD, but do the filters come into play with any of the planetary stuff?

Pamela: They can if you’re trying to accentuate filter, when you’re trying to accentuate features, but they aren’t going to help you get that true color image. Now, what you can do is if you’re in a very light-polluted area, there are some filters out there that specifically try to filter out the light produced by sodium lights, that specifically try to filter out some of the other compression lights. As we use more and more fluorescents, it makes it easier in some ways to filter out the light using narrow-band filters, but in general, if you’re trying to get a pretty true-color image, you’re not going to get it with filters. If you’re trying to look at specific features, if you’re trying to pull out the icecaps, pull out the valleys, that’s when using the filters can help.

Fraser: And I know that some people use this technique for observing the Sun, and so obviously then you definitely want to get some solar filters.

Pamela: Yeah, you don’t want to look at the Sun at all without a filter, and so there you’re looking at one of basically two different things. You can get what’s called a neutral density filter, which blocks all colors of light equally, and so you can get a neutral density filter that blocks 90% of the light in all wavelengths. You probably want to go even more than that when you’re looking at the Sun. Now, the other direction you can go is you can get something called an H-Alpha filter, and that’s a filter that only lets through the specific transition called H-Alpha in the hydrogen atom. This is one of the bomber lines; it’s the one that allows you to see all of the neat corona, loops, and storms, and it accentuates sunspots, and if you have enough magnification it actually allows you to start seeing the convective cells on the surface of the Sun. Now, if you just go with a neutral density filter, all you’re going to see is the sunspots and the bright stripes, the faculae that are caused by coronal loops, but with the H-Alpha you can start to see details in everything.

Fraser: OK, so I think we’ve kind of wrapped up the techniques for that second method. And the third method, and I think this is the one you know the most about, is the deep field, you know, big telescope, CCD camera connected to it…how on Earth do people get these amazing photographs?

Pamela: Lots and lots of patience and tracking, and the really, really best ones – what you’re actually doing is you’re sitting there, and you either have a second CCD chip that’s auto-guiding your telescope, or you’re sitting there with a hand paddle guiding your telescope as you watch a video screen output. It’s like playing a video game of keeping the star on the target. Nowadays, a lot of times the software will do it for you, but when I was a graduate student, there was hour after hour of moving the telescope… Literally, you’re pressing buttons, and it’s just like the slowest-paced video game EVER. So you’re making sure you’re staying precisely on the star, or on a bright object in the field that you can put crosshairs on to make sure that you’re staying focused, or staying pointed. You perfect focus, you very slowly step through and make sure you can’t move a hair in either direction without making your stars become bigger blobs, so once you get your focus just right…and you can’t…you actually have to be careful that you don’t end up with square stars. This is going to sound really strange, but if you’re on a telescope with a really large field of view and the atmosphere is perfect, when you get the telescope completely in focus as perfectly as it can be focused, sometimes the stars are one pixel in size, and that is unappealing and you can’t do anything with it scientifically, so there are actually rare cases where you have to un-focus your stars slightly to make sure that they spread out across enough pixels. So it’s this black art of if the stars are big enough, focus the telescope so they can get no smaller. If you do that and you have square stars, un-focus. So you play with focus, get it perfect; once it’s perfect, you then start taking exposures. You want to have your exposures long enough that the sky stays black, but you’re starting to get whatever faintness that you’re looking for, whatever nebulosity, whatever arms on a galaxy, and you’re not getting too many cosmic rays, so usually the longest you want to try and push is about 900 seconds for a perfect system. After 900 seconds, the number of cosmic rays just becomes annoying. Most systems you actually want to stay down around 300 seconds, so you get those 300-second exposures, and you do it one filter at a time. With these high-grade CCDs, the way you get extremely good resolution is all of the pixels are simply sensitive to light/no light, and so everything you do is black and white images. If you were getting color images, there’d actually be triplets of pixels that are sensitive to the red/green/blue of a color CCD. You get more resolution by doing black and white, so then to get color, this is where the filters come, so you actually put the red filter, the R filter, the whatever filters that you’re using filter on, take the exposure. You then put the next filter on, and here’s where it becomes a black art because your CCD is differently sensitive to light in different colors, so you might find, “Oh! Everything is starting to saturate! I’m starting to get to the point where I’m blowing out my CCD at 200 seconds in red. Now, I put the green filter on and — oh, crud! At 250 seconds I’m starting to saturate!” So you have to figure out how do you play with the exposures, and that’s also going to vary with, well, what are you looking at? Is it a blue galaxy? Is it an oxygen-rich nebula? Is it a red reflection nebula? All of these different (or a red transmission nebula, rather)…all of these different things you have to adjust your filters, you have to adjust your exposure times for.

Fraser: Wow! That’s like way more complicated than the other methods. It’s funny how it all scales up. The gear’s more expensive and the method is a lot more complicated, but at the same time, you know — greater risk, greater reward. I mean, you see some of those pictures, again, some of the best…guys John Chumack, there’s a lot of them, Tom Davis… they produce these photographs that look like they came from the Hubble space telescope. Their ability, their technique is so good that it’s just astonishing. So they are targeting that sweet spot, that you have the CCD hooked up, you get your filter on, you capture for 300-ish seconds and then store that image, that long-exposure image, but it’s going to be like take one image, and then take another one, and then take another one, and then take another one, and then we’ll talk about technique next week, or I’m sorry, about post-processing, but essentially you’re stacking all those images together try and just keep…you’re taking long-exposure after long-exposure and then creating a super long-exposure with all of those together, and if you’ve done your job right, you’re going to get those beautiful faint, the nebulosity, the galaxy, the dust in the galaxies and all the beautiful pictures that come with astrophotography.

Pamela: And if you’re just after pretty pictures, one of the really awesome tricks I learned from an amateur astronomer (because you can’t use this data for science) is one of the tricks for bringing out all the details is remove the filters — all of the filters — from your camera, and create what’s called an illuminance image. This is where you just capture as much light as you can to get the details, and then you use that as a mask in your final image, and if you’re struggling to get enough light of a really faint object, when you then put your filters on, you can do what’s called binning the CCD. This is where you combine the light that’s hitting every four pixels into one, so that’s a two by two bin, or you bin all the light that’s hitting every 16 pixels into one – that’s a 4 by 4 bin, and this allows you to get deeper images faster, and that’s particularly useful if you’re just not that sensitive a set of equipment. So you then put your red filter on, bin your CCD get all of your red light, put your green filter on, bin your CCD get all of your green light, and when you stack it together later, you’re able to resurrect all of that detail using that illuminance frame. Now, if sensitivity isn’t an issue, then you go the other direction, and you just do everything through filters, and you start playing with what are called narrow-band filters. There’s two types of filters: there’s broad-band filters and there’s narrow-band filters. Broad-band filters are like, “I want all the shades of red. I want all the shades of green.” Narrow-band are, “I want the light produced by the H-Alpha transition. I want the light produced by the specific oxygen lines produced in planetary nebula that are green.” And here you’re looking to bring out specific scientific neatness, awesomeness details by which filters that you’re using.

Fraser: Yeah, and the terrible truth of astrophotography with a lot of the scientific stuff, the stuff from Hubble, is the pictures are completely fake. They’ve, you know, they’ve used one very narrow-band filter for one color, they’ve used another very narrow-band filter for a completely different color, and then a third one, and then they go that one is red, that one is blue, and this one is green, and then they merge them together and you get a…what looks like a beautiful colorful photograph, but actually has nothing to do with what the object really looks, and again, I think, this comes down to your experience. Are you trying to create a realistic view of what the object really looks like, or are you trying to create a very beautiful picture? And if you’re trying to create a very beautiful picture, you’ll want to learn which of those narrow-bands are going to give you the right combination of colors to make your image look beautiful — and you will be part of the lie.

Pamela: [laughing] Well, it’s not always a lie, sometimes it’s…

Fraser: No, it’s not always, but I know with a lot of the stuff with the Hubble and stuff that they aren’t going for true color.

Pamela: Right. Right. What I love though is sometimes the universe just works and a lot of these nebula where you’re looking at specific emission lines of gases, you get your oxygen narrow-band filter and that’s green, and really that’s all the green the nebula’s producing. You get your hydrogen filter, and that gets you the red, and really that’s all the red that’s being produced, and by using these narrow-band filters, you’re able to basically get rid of a lot of the background goop, and strictly see the light of the nebula.

Fraser: Very cool. Well, I think next week we’ll go into the whole other half of this project, where you sit with a computer and process, process, process to get those final products that people see, so that’ll be great. Alright well, thanks a lot, Pamela.

Pamela: That sounds great. I’ll talk to you later, Fraser.

This transcript is not an exact match to the audio file. It has been edited for clarity.

Ep. 239: Astrophotography, Part 1: The Gear

admin — Wed, 23 Nov 2011 22:45:10 +0000

No matter how good your telescope is, you’re never going to see the same detail and colours as the photographs. To take amateur astronomy to the next level, you really need to attach a camera to your telescope. Welcome to the hobby of astrophotography. Fair warning, this hobby could bankrupt you.

Ep. 239: Astrophotography, Part 1: The Gear

Show Notes

End of the World…. (Not!) Cruise
The World At Night (TWAN)
Nikon Vs. Canon DSLR cameras for Astrophotography — AstroPix
Tripods/Mounts for Astrophotography – AstroPix
Oceanside Photo and Telescope
Aperture and shutter speed — Cambridge in Colour
Lenses and Zoom for Astrophotography – AstroPix
Webcam Astrophotography Tutorial for Planets – Ray Shore
Using Webcams for Planetary Astrophotography — Schmidt-Cassegrain website
Clay Center Observatory
Ice In Space
Mike Salway
Thierry Legault
Guide to CCD Imaging — Starizona

Transcript: Astrophotography Part 1: The Gear