Transcript: Mysteries of the Solar System, Part 2

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Fraser: Astronomy Cast Episode 175 for Monday February 1, 2010, Mysteries of the Solar System, Part 2. Welcome to Astronomy Cast, 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's it going?

Pamela: It's going well. How's it going with you, Fraser?

Fraser: Good… ready for more mysteries. So apparently, this is at least a two-part series. We have no idea how many there's going to be. But this week, we continue examining some of the baffling mysteries of the solar system… where we fill your head with more questions than answers. Sometimes we've just got to share the enjoyment of not knowing the answers. Alright Pamela, so we… when last we saw our heroes they'd covered Pioneer, Uranus, Europa's seas, methane on Mars, strange atmosphere on Titan… so, mystery number six: How does the sun's corona work? Why is it so hot? So what's a corona?

Pamela: It's the highest level where you start seeing the beautiful loops, the beautiful flares, all of the amazing activity that missions like STERO and… well, our new little SDO is going to be imaging these as well.

Fraser: Right, so these are all these crazy plumes and prominences coming out of the sun… that's the corona. And it's hot.

Pamela: It's too hot. It's pretty much the same temperature–like 15 million degrees-ish–as, well, the core of the sun.

Fraser: Right, so the corona–the outside of the sun–is the same temperature as the core of the sun… which is hotter than the surface of the sun, which is only like 5800 Kelvin.

Pamela: Yeah.

Fraser: So, how is it possible that you can have… I understand that the core of the sun is 15 million degrees Kelvin, the surface is only 5800 degrees Kelvin, and it keeps getting cooler from there… but, no, the corona is back to 15 million degrees.

Pamela: Yeah.

Fraser: Now it's not like, you know… go out and roast in the 15 million degree temperature… I mean the pressure… there's so little material out there that it's not like fusion is taking place.

Pamela: So, here's what's happening. The material… it's really, really thin. But when you start looking at it with missions with ever-so-boring names like the NASA-funded X-ray Telescope… very blandly named instrument, or the Extreme Ultraviolet Imaging Spectrometer, also very blandly named instrument, both of these on the Henoday spacecraft, you start seeing that there's plasma that's 10 million degrees Kelvin, there's plasma in other places that's 5 million degrees Kelvin… we're looking at all the different loops and measuring the temperature… so the material tied up in the loops… and we can't really explain what's happening, and that's never a good thing. It was originally thought… and Ian O'Neill who writes for Universe Today is one of the people who worked on this model… that perhaps there's some sort of steady state heating where you have these giant loops and they're able to conduct heat up, and it's this conducted heat that's steadily, steadily increasing the temperature, increasing the temperature, increasing the temperature. But the models that make those predictions predict that the loops are going to have a certain density, and they don't. And that's a bit problematic.

Fraser: So some process is boosting the temperature of this material back up again, and there's no real good answer yet.

Pamela: So, the other thing that we blame it on is nanoflares, but we're just starting to be able to observe nanoflares. So, we're not sure if that's right either. So this is one of those cases where we have more models than we have evidence. Hopefully soon we'll know.

Fraser: So you just mentioned that the SDO has just launched…

Pamela: Yes.

Fraser: Is that going to help?

Pamela: Well, the one thing that it will be able to do is constantly monitor the sun's activities at a cadence, a rate, that we've never seen before. It's going to be taking image after image after image after image, firing them back to the planet Earth… tidal wave of data coming back at us in a resolution that we haven't seen before. And hopefully, by getting flooded in data, somewhere in all this new information, the solution is going to be found.

Fraser: Question number seven: What is the cause of the Kuiper Belt cliff? So the Kuiper Belt is an area of icy objects surrounding the sun… starting from the orbit of Neptune and out… large objects in this group are Pluto and Eris… so, why does it start and why does it end?

Pamela: Well, the starting is a little bit easier. It couldn't really have formed anywhere earlier in the solar system.. it was either too warm, and you ended up with an asteroid belt instead… too cleared out by Jupiter, which is very good at herding things into little pockets of Trojan objects, Saturn's another object that's pretty good at clearing up the space around it. So, where the Kuiper Belt starts is pretty much where you'd expect a belt of icy bodies to maybe start being able to exist. But the problem is, is that it's thought that they should just keep going, and they don't. We know that we don't have them further in because of resonances, we know that there's empty holes where the objects would be in resonances with some of the other planets that are emptied out. Then, suddenly, about 50 astronomical units away from the sun, they just drop off in number. And they shouldn't… they should actually be increasing in number according to models. So, the idea of a planet being out there really isn't one that we're all embracing quickly, but it is one that's been mathematically worked out by a researcher named Patryk Lykawka and if he's right, then there could be another planet out there… something the size of Earth or Mars that's responsible for clearing out this area of the Kuiper Belt.

Fraser: Where's the planet?

Pamela: We don't know…

Fraser: We would see it, right? If we've discovered Eris… it would be further out than Eris, right?

Pamela: It would be further out… so we're looking for something that would be further out. We don't know how dark it is, if you have something that big it's probably… well, we don't know… we can't say anything about it, but it could be covered in substances that make it non-highly-reflective. It could just be we haven't managed to stumble across it yet.

Fraser: But it would be… it would be pretty big.

Pamela: It would be the size of roughly Earth or Mars. But if you have something out there that's slow-moving, and this would be slow-moving, that's extremely faint because it's not very reflective, it could've gone missed at this stage. So this is where the Large Synoptic Survey Telescope potentially will be able to start finding some of these really faint, really slow-moving objects that are out on the edge of the solar system while it's turning up everything else.

Fraser: So, is it possible that the Kuiper Cliff is actually more of a divot, that we see the end of the cliff and there could be some great big planet orbiting in that spot, and then on the other side of that planet's gravitational influence, there's more icy objects.

Pamela: It's entirely possible.

Fraser: And then we just can't see them, we're already working at the very limits of Hubble to even see some of these Kuiper Belt objects at all.

Pamela: Right. Right. And so the confusing thing that we're in right now is, yeah… there could be a divot out there, and in fact, all of our theories suggested that the number of objects should increase by as much as a factor of two beyond 50 AU instead of dropping to zero. So, it could be that there is an object out there that's dark and orbiting slowly that we just haven't seen, and that there's more objects hiding behind it.

Fraser: Hmmm… it's a mystery. Who knows the answer? We don't! Alright, number eight… Why do long-period comets come into the solar system?

Pamela: Yeah, we don't know that one either.

Fraser: No… we have the short-period comets that are really just Kuiper Belt objects that have been shoved into a more… a different orbit where they come in, but they don't go out too far. They come in to the sun and they don't go in too far. But there's this whole class of objects that come in almost like they're coming in on a straight line… the size of their orbit is so big, and they can take tens of thousands of years, millions of years to make a trip around the sun. What on Earth… or what on space… where are they coming from? Why are they coming towards us?

Pamela: Well, we're pretty sure we know where they are coming from. They seem to be originating from somewhere… probably between 20,000 and 100,000 astronomical units away from the sun. They're starting really, really, really far away. But, what we don't know is what sent them our direction. So, there's this cloud of material that we call the Oort Cloud that we believe… and there's some evidence based on looking at alterations to the cosmic microwave background that we can actually see what in some ways might be regarded as the shadow of the Oort Cloud… We're pretty sure the Oort Cloud's out there. We don't have direct evidence, but we're pretty sure it's out there. Something is causing objects to get knocked out of the Oort Cloud and sent our direction, and it could be that we periodically pass close enough to other stars that objects get knocked in. It could be objects interact with one other periodically and something gets sent in, it could be there's a giant planet on an elliptical orbit or a… maybe we have a brown dwarf or a red dwarf companion star that just hasn't been found. And any of these additional bodies could knock things up in the Oort Cloud and send a rain of icy material into the inner solar system.

Fraser: And one of the theories is that it's these rains… these periodic rains of comets that have caused some of the big devastation on Earth in the past, that seem to come every 65 million years or so, right? With the last one occurring about 65 million years ago…

Pamela: Exactly. But, even ignoring these giant infalls of material, we still get 5 to 10 fairly significant cometary bodies coming in to the solar system each year. So, yeah, we get giant influxes on a regular basis, but we're also getting things on a steady lower level all the time.

Fraser: So the question is, what is the thing that kicks them out of their nice stable Oort Cloud. Why did they choose now… out of the 4.5… 4.6 billion years they've been orbiting the sun, why did they pick now or 10,000 years ago to fall into the inner solar system?

Pamela: And all different possibilities we have are ones that… if you generally see an article that says "Giant planet suspected to be orbiting edge of solar system," you'd call the person a crazy… "Sun thought to have binary companion," you'd think the person a crazy. But, the only way we can start to explain this is to invoke these theories, and it starts to get kind of uncomfortable. It's almost like an angry gremlin kicking them into the inner solar system is just as valid a theory, but you can't mathematically justify that. So, it looks at one level really like there could be something out there.

Fraser: But… it has nothing to do with this Nibiru nonsense… Planet X…

Pamela: No. Nothing. Nothing at all to do with any of that.

Fraser: So, mystery number nine: Why does Enceladus have geysers? And this is amazing. This is one of the big discoveries of the last 5 years… which is that Cassini has discovered these geysers of water-ice blasting out of the southern pole of Saturn's moon Enceladus. So if there's a geyser of water-ice, then does that mean that there is a hot bubbling water pool that's spewing out water that's turning into ice as it reaches space? So, what's going on here?

Pamela: Well, what we know for certain… because we can image it… is that Enceladus has geysers, that they're shooting sprays of water out of the surface with escape velocity. This is actually helping to feed into some of Saturn's rings and to keep replenishing them with new material. And then trying to understand it, there are competing theories. There are groups saying that there are underground oceans that perhaps the pressure from the oceans… the water's mist is coming up through the surface and sending out this high-powered mist in some ways.

Fraser: Right, but it's the same situation… it's a tidal flexing going on… an interaction between Saturn and Enceladus that is causing it to remain liquid inside and heating up the liquid, and then that liquid is being spewed out of these geysers. Sorry to derail you, but I think it's kind of funny that one mystery about Saturn has been solved by this, and yet it creates a brand new mystery.

Pamela: I know, I love it!

Fraser: What is one of the possible sources replenishing Saturn's rings? Oh, well it's the geysers on Enceladus… the wha?! The geysers on Enceladus? Yeah, I know… that's what it is. Sorry, so what's the other… you said maybe it's bubbling water?

Pamela: Maybe it's underground oceans… there's other groups that are claiming–well maybe there's caverns where this is taking place… all sorts of crazy geometries of the underground geophysics are being invoked… and they're not really crazy. They're all
geophysics that exist here on earth.

Fraser: And I've seen some dry… some not-water… not-liquid solutions for it as well. Which are just ice being rubbed together… sublimated… and it's just coming out as geysers. So it's not actually liquid, it's just ice, because Enceladus is almost entirely ice.

Pamela: Right, so you basically have cryovolcanism. But the real question starts to be that Enceladus, as far as we know, isn't all that different from the other icy moons. Why don't all of them have geysers? So this is really a two-sided problem. Not only why does it have geysers, but why don't the others as well? And we don't know.

Fraser: But they might… I know they've found like hints of some similar process going on with Rhea and Dione as well. So, they haven't ruled it out yet. They've found particles. I forget what it is… like hydrogen atoms surrounding those moons, but not in the same way that you see it around Enceladus.

Pamela: So, we need to just keep looking, and keep trying to understand it. And maybe send another robot.

Fraser: But as I said, that is a classic example of like… one problem solved… ten! ten mysteries open up…

Pamela: And throw out one problem and get back ten theories.

Fraser: Yeah, exactly. Ok, mystery number ten: the hexagon on Saturn… hexagon on Saturn? What's that?

Pamela: Right, oh… if you haven't seen a video… any of you out there listening to my voice right now… if you haven't seen a video of Saturn's hexagon in motion…

Fraser: Google it!

Pamela: Yes, there's examples of it on Wikipedia… easy to find. It's this amazing structure that's a perfect hexagon. It's not something where you're eye is tricking you into thinking… well, maybe there's something vaguely stop-sign-shaped… but, no, it's a perfect hexagon.

Fraser: There's a bolt… there's a great big bolt on the bottom of Saturn that you could take a great big wrench and crank it. That's what it looks like.

Pamela: And the straight sides on this thing… they're basically 14,000 kilometers long.

Fraser: That's a big wrench.

Pamela: Yeah, you'd need a really big wrench… really big handle to turn it, as well. This entire thing is being turned by an invisible wrench at the same rate that the planet seems to be rotating… a little over ten hours. So, lots of people have been trying to figure out exactly what this is. It has basically a clearly-defined hurricane-like eye wall that's a hexagon rather than the perfect circle that you get with a hurricane.

Fraser: It should be a circle… by every piece of physics that we know, and atmospherics, that should be a circle.

Pamela: Yeah. But it's not. And so when you see things that you don't understand that are waves that are not changing, you call them standing waves. So, it's been possible in the laboratory to spin buckets of just the right fluids in just the right ways to get polygons. There's all sorts of really cool experiments where they spin things under different conditions and sometimes they actually take giant globe… put giant globe over it and fill the space between the two giant globes with different fluids that mix in different ways, and they try and create planetary atmospheres this way, or at least the motions of planetary atmospheres. And we can get polygons, by spinning things in just the right way… but not hexagons… and we haven't seen exactly this shape. There are some people that think this might actually be tied in somehow with Saturn's aurora. So, time will tell… more observations are needed.

Fraser: Does it have one on the other hemisphere?

Pamela: No… at least not that we've imaged yet. So far in all the images–and this has been seen by both Cassini and by the earlier Voyager mission–there's a northern pole hexagon.

Fraser: Do we see this on any of the other gas giant planets?

Pamela: There's something similar on Venus, but it's not identical. It's another giant
hole through the atmosphere generated by the spinning winds.

Fraser: Right. But we don't see an even bigger one on Jupiter…

Pamela: No.

Fraser: Jupiter provides the circle that we crave.

Pamela: Or at least behaves more rationally.

Fraser: Yeah, exactly. So, who knows why it's there? We don't know. It's a mystery. Sorry… Well, I think we got through another set of five and who knows… to leave you with one more mystery… next week, will we continue on with mysteries 11-15? Or start our first set of mysteries about the Milky Way? Who knows?

Pamela: This is our mystery to you…

Fraser: Or to us… 'cause we haven't figured it out yet…

Pamela: And one final announcement, though. We forgot to tell you at the beginning of the show… we have new toys for you in the Apple store.

Fraser: Oh, right! Yes… yes….

Pamela: Wizard Libsyn Systems… our hosting provider… put together for us an iPhone app. So, if you're an iPhone owner, you can go out and buy an app that will bring to your phone the latest shows, and we're going to be getting all of our transcripts into it. It's $1.99 and we do get proceeds from this, so there's yet another cool way for you to get and consume all of the Astronomy Cast content.

Fraser: Right. So this is like a separate app, apart from what you would download in iTunes. So, check it out, and if you want… yeah…. $1.99. Well, thanks a lot Pamela, and we'll talk to you next week.

Pamela: Sounds great Fraser… talk to you later.

Transcript: Mysteries of the Solar System, Part 1

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Fraser: Astronomy Cast Episode 174 for Monday January 25, 2010, Mysteries of the Solar System, Part 1. Welcome to Astronomy Cast, 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're you doing?

Pamela: I'm doing well Fraser, how are you doing?

Fraser: I'm doing great! So this week… well, we know a lot about our solar system, and there's an awful lot that is a complete and total mystery. Today we're going to begin a series of unknown length examining some of these mysteries and explain the best theories that astronomers have so far. So I think that one of the problems that we do is that we kinda come up with an idea for a show, and we have a schedule, and I'm often rushing Pamela to kind of meet the schedule, meet the time. Well, I'm not going to be time's slave anymore… so we have no idea how many part series this is going to be. Could be a one-part series… but, you know, more likely no… it'll probably stretch on further. But, it's so cool… and you know what's kind of interesting is… now, I'm kinda going off on a tangent–sorry… my daughter is studying space and astronomy in her school, and I'm going to come in and give a presentation to her class that is essentially the podcast we're going to do today, which is a collection of crazy mysteries in the solar system and the best ideas that we have. But I get to show pictures to the class… you'll just have to use your imaginations… or follow along on the web as you go… so, let's get on with it! These are big mysteries in the solar system… in some cases astronomers have some idea of what we're talking about… in other cases–no idea. Should we start with the Pioneer anomaly?

Pamela: Let's go ahead and start with that. It's kind of the oldest of the mysteries, I think.

Fraser: Alright, let's do it. So, in case you weren't aware, there is a weird situation where the Pioneer spacecraft aren't where they're supposed to be. So what's going on?

Pamela: Well, as they're moving out towards the edge of our solar system, as they move out towards leaving our solar system we have calculations on how much they should be slowing down as they go because the sun and the solar system's gravity is pulling on them, we have calculations on… ok, we fired the rockets here this amount… We should know everything about how these suckers are moving through space. We know that there might be some factors to correct for… they fire off radio transmissions toward Earth–that might have an effect. They get heated up by the sun–that might have an effect. And when you put all these pieces together and you figure out where they should be–they're not there. It turns out that for reasons we can't really explain–and this is true for Pioneer I and Pioneer II–both the missions seem to be slowing down more than they should be, and we can't explain it.

Fraser: So, they're not as far from the sun as we would expect them to be.

Pamela: Right.

Fraser: And even when you plug in Newton's formulas for gravity and then you try Einstein's formulas for gravity and you include all that stuff–the additional push of them using the radio transmitters… that's a pretty weak amount of push that they must be getting–they're still slowing down too quickly.

Pamela: Right. And the thing is, all of these things that we've tried to blame the Pioneer anomaly on–the fact that that they are using their antennae to blast radio signals… that should be accelerating them away from the solar system, the fact that the sun is heating them on one side and not the other… that should be pushing them away from the solar system… So, for some reason those things aren't pushing them out of the solar system, or at least there's something else keeping them in the solar system with an even stronger force. And all we can really do is go over the numbers again and start scrutinizing how we built the missions. And the crazy thing is, within error, it looks like we might have the exact same results for the Cassini and Galileo missions as well on their way out to Jupiter and Saturn.

Fraser: What about the Voyagers?

Pamela: The Voyager missions… and now we're going to hopefully have New Horizons as another case study to look at. But we're not sure how to explain how these different missions all have, with their different architectures, seemingly the same anomaly. Now the thing is so far, Cassini, New Horizons, and Galileo haven't gotten that far out and we have a completely different design for those missions than we have for the older ones. And we also, more importantly, have a different way of transmitting and storing the data. And one of the things that's being scrutinized is are changes in how we look at the data… are those differences over all the years and all the different format changes–are those the responsible party? Or does it actually have something to do with the spacecraft and its fuel cells perhaps giving off heat in one direction but not the other.

Fraser: And so it's either a measurement error…

Pamela: Yep.

Fraser: It's an unknown… sort of something going on with the spacecraft, some interaction that we're not thinking of, like…

Pamela: One side is hot due to the fuel cell, and that side is the one that's away from the sun and that heat from the fuel cell is creating a force.

Fraser: Or, it is deep and fundamental… that there is some understanding of basic physics of about how things move in space over long distances that we just don't understand.

Pamela: And that's the most painful one to deal with because when we look at the orbit's of the Kuiper Belt objects—they make sense. When we look at the orbits of Uranus and Neptune–they make sense. When we look at the orbits of even all of their moons–they make sense. So, whatever it is, if it is fundamental physics, is only working on this radial axis from the sun, and it's not affecting things orbiting the sun. And that just seems crazy.

Fraser: So, things moving away from the sun experience this thing… whatever it is. And it could be, you know…

Pamela: Just the way we built the suckers causes them to behave differently… that could be it.

Fraser: Right. And this is one of those things… it's so great because it's so simple. It could be either… oh, yeah, we have a slight modification to our math… oh, we wrote down the numbers wrong, or we don't understand gravity… you know…. It's quite a wide range of possibilities, so… anyway… so that's it–mystery! We don't know… stay tuned! So, mystery number two–the strange axes of Uranus and Venus. So, Venus is flipped completely upside down, so…

Pamela: 177.3 degrees off of normal.

Fraser: Right, so imagine you take the earth spinning… you flip it upside down but still keep it spinning in the same direction… from your perspective looking at the planet now… it's going the wrong direction. Venus rotates backwards to all the other planets in the solar system. Uranus has just been rolled only onto its side, so, you know, sometimes it's pointing its south pole at the sun, and other times it's pointing its north pole at the sun, and… you know… is spinning on its side.

Pamela: It's tilted 97.7 degrees. So neither of them are quite dead on… but, wow they're close.

Fraser: So what is up with that?

Pamela: Well, we don't quite know.

Fraser: Right, the earth has an axial tilt of 23.5 degrees… Mars is kinda similar… Mercury is kinda similar… Jupiter, Saturn, they're all close to that.

Pamela: So, we have two different mainstream theories. The first is that in both cases… take a planet, whack a planet with another planet, and it flips over. With Uranus, that starts to get a little bit troubling because you need to get things really big to hit it, and we just don't know if there was anything that big hanging out doing the colliding back then.

Fraser: But couldn't just time do the trick for you? You hit it with something… I don't know… Mars-sized, and then you just give it 4.5 billion years to roll over?

Pamela: No, because these things tend to either keep rolling once set into motion–it's "things in motion stay in motion" that's a problem–or, once you whack it, it just stays put. That's the way it normally works out is you just whack something into a new stability. Rotating objects are very consistent in keeping their axes pointing in one direction–this is how gyroscopes work on space stations, on spacecraft. Without this characteristic of spinning objects, we wouldn't be able to move spacecraft around. Planets are just spinning tops, they're their own form of gyroscopes so they're spin-stabilized is one way to think of it.

Fraser: Right, and here on Earth we have the precession, right… where we have a bit of a wobble, but that wobble stays within that very specific range, and so you still have the wobbling of the top but it's not like it wobbles over to one point and then just stays there… it's always kind of moving back and forth and back and forth.

Pamela: And so here… it could be that we played "Whack-a-World" but the other option is…. well, maybe this is just tidal effects, maybe this is resonances. One of the things about the formation of the solar system that people are playing with is it's hard to explain how to explain how Uranus and Neptune could have formed where they are located today. But, what is easier to imagine, is that all of the gassy planets, all of the two ice giants and the two giant gases–Jupiter and Saturn, Uranus and Neptune–what if they all formed closer to the sun but Saturn and Jupiter hit a resonance where their resonance caused all sorts of crazy things to happen. There are several different ways of modeling this that start out with all four planets basically tumbling in a gas-giant ball and then moving apart and you basically end up flinging Uranus and Neptune out to the outer solar system. Other cases they start out as four distinct orbits but Saturn ends up on a more and more elliptical orbit over time due to a resonance with Jupiter until it finally settles into an almost circular much larger orbit and in the process also flings Uranus and Neptune out to the outer solar system.

Fraser: So it's almost like you need one process to start the movement and then a second process to stop it. You need the start, and then you need the brakes… to kick on the brakes again to make it stop.

Pamela: And this is where ending the resonance is essentially putting the brakes on.

Fraser: Right, right. Because, I mean, we have examples of asteroids that are tumbling in two directions… they're rotating and they're also tumbling because… and they'll never stop because nothing's ever stopping them from doing the tumbling part.

Pamela: Right. And with Venus it's thought that maybe some sort of a chaotic process where it was getting gravitationally beat up by the planet Earth in some ways was what got it into its situation. If you look at how long its day is… it's a resonance with how often Venus and Earth and the Sun all line up into a nice straight line. So it's possible that this is just the pull of gravity over time gradually tilting and tilting and flipping through all the different resonances in the solar system. Venus just happened to be the one that was susceptible to being put on its head.

Fraser: So why are Uranus and Venus… they're axial tilts off the plane of the ecliptic? It's a mystery. Alright, mystery number three… what is underneath the ice on Europa?

Pamela: Hopefully water.

Fraser: Hopefully water… right, so once again, we've got the situation where Jupiter has its four Jovian moons: Io, Europa, Ganymede, Callisto, and the tidal flexing from the gravity of Jupiter is kinda squishing these moons and then… keeping them softer than they ought to be. With Io, it's full-blown volcanism with huge… magma and lava coming out, with Europa it's not quite as devastating, but you can see… astronomers are pretty certain that there's a shell of ice and underneath that is a great big liquid water ocean… maybe?

Pamela: Maybe. And this is what we're hoping. What we do know is that when you look at images of Europa, it's one of the most beautiful moons in the solar system, I think, it in many ways looks like some sort of a blown-glass ball covered in cracks in the glaze. It highlights in blues and in oranges in many of the different Galileo images. This strange little icy world is actually the reason that we plunged Galileo into the Jovian atmosphere. This moon, through cracks in its surface, is constantly resurfacing. What this means is craters that form on Europa don't get to stay there. They instead get filled in. Basically, a geophysical Zamboni is constantly clearing the ice of Europa.

Fraser: I was going to use the Zamboni reference! That's exactly what it is, right? Every now and then the ice gets all smoothed over again.

Pamela: Right, and the easiest way to explain this is the Zamboni method…. you just spray the sucker with liquid and the liquid refreezes and you're back to a nice smooth surface.

Fraser: And where's the spray coming from?

Pamela: And that's the question… we don't see it directly, but more likely we simply have this slow coming-up, this slow puddling… more like what you see if you go to Yellowstone and visit the bubbling mud pots than if you go and visit the geyser of Old Faithful. So somehow liquid is coming up to the surface, and if liquid is coming up to the surface, that means there is liquid below the surface.

Fraser: Right.

Pamela: And the models… some of them say the ice is a kilometer deep, some of them say it's tens of kilometers deep… but no matter how deep it is, there's probably an active rocky core underneath that's doing the heating.

Fraser: Io… what's happening to Io is happening to the core of Europa… it's being flexed and heated, and putting out heat, but it's not turning into great big plumes of lava… it's just keeping this ocean warm.

Pamela: And the amazing thing to think about–and there are a few papers related to this–is it could be that you have mid-European ocean volcanoes and basically lava plumes just like you find in the deep trenches here on the planet Earth. And it's those deep ocean plumes that are so rich with life that never sees any sunlight, so we know that this form of volcanism under water is capable of supporting life. This makes people wonder, very honestly, could there be life supported under the ice on Europa?

Fraser: Yeah, people don't realize you could destroy the sun and there would still be life on Earth.

Pamela: Until it cooled off…

Fraser: Until it cooled off, but for billions of years you would have the geothermal heat heating the oceans, keeping life going… no problem. So, who knows what's under there… Now, is there going to be any way that we're going to know? I know there were ideas to send a probe that could melt down through the ice and try to make its way down to the ocean.

Pamela: Like so many problems, this is one that comes strictly down to money. There are robots being designed and tested right now that, if you drop them into an underground lake, are capable of going down and on their own exploring and mapping what exists down beneath the surface of the planet Earth. Then they come back and they radio their results. So what we need is to develop a robot that takes this one step further and digs a hole for itself through the ice and drops itself into what is hopefully not too far down… liquid water, and then digs itself back up to the surface and beams its results back.

Fraser: Or, leaves a tether behind, right… some kind of communication tether… it leaves that up on the surface, melts its way or bores its way down through the ice, gets down to the ocean, leaves that as a way to communicate and then travels down into the ocean to see what's below. It's a monumental engineering challenge to make that work.

Pamela: And beyond just the budget difficulties, anything that's swimming around underneath the ocean of Europa… or underneath the ice of Europa, rather… won't be able to use solar panels. To continue exploring the outer solar system, and to explore places where literally the sun doesn't shine, we need to use radioactive fuel cells, we need to use radioisotopes. Right now, here in the United States, we have a shortage of these. We're simply not developing the fuels that are needed to power spacecraft. A lot of international treaties govern what nuclear isotopes you develop and you process and you refine and all those other different things. And under treaty, it's unclear if we can create fuel cells we need for our space program.

Fraser: So, who knows… this is one of those situations where I'll bet you someone's going to come up with a clever way to analyze the ice on the surface and detect evidence of life's outputs… right? Micropoop in the ice on Europa… so we'll stay tuned on that one…
Ok, so next… mystery number four… what is creating the methane on Mars?

Pamela: Yeah, we don't know that one either…

Fraser: No, I know… but this is huge!

Pamela: This is one of those amazing discoveries!

Fraser: Yeah, so once again, to set the scene… the European Space Agency's Mars Express spacecraft discovered the faintest whiff of methane in the atmosphere of Mars. This is really shocking and surprising because methane is destroyed by sunlight in a very short period of time so there has to be some source replenishing the methane. What's creating it?

Pamela: And during the northern summer, they were actually finding as much as 30 parts per billion of methane in the Martian atmosphere, and methane is something that gets actively destroyed by the sun. Sunlight… ultraviolet light hits methane… methane stops being methane, it's happy to do that. So this is something that's being actively produced, and we only know of two sources of methane.

Fraser: Source number one?

Pamela: …is lava, geophysical activity, something indicative of the planet being alive geophysically.

Fraser: And that would be very exciting to discover… we could see Olympus Mons erupt again…

Pamela: I'm not quite sure we could go that far… but it does mean that there is some sort of process going on that–well, it's always cool when rocks are alive–but the other process is… well, life produces methane. Meet a cow–you've met a methane-producer. Small biological entities, bacteria, single-celled organisms in all their different forms, there's many different ways to produce methane and so if Mars is as geophysically dead as we've been teaching for, well, as long as I've been alive, that means that there's methanogens or some other form of methane-producing life in Mars.

Fraser: And, I mean, if they can find that, the ramifications of that are gigantic. That means that there's life on Earth and there's life on Mars. And if there's life on two planets, then life could be all over the place in the universe. And you would, in theory, eventually be able to find the source and be able to study it and see if the two are connected. Did life begin on Earth and separately on Mars, or are they somehow interconnected? Do they share a common ancestor? The ramifications of this are mind-boggling. Now there are plans to get to the bottom of this mystery.

Pamela: Yes, and everything from the upcoming Mars Science Laboratory to most of the plans for the future for Mars all include going and digging in the surface and looking for signs of life. One of the most exciting ideas that I haven't seen any missions attached to yet, is going and… there's several different places that we've seen along the volcanoes on Mars skylights into deep dark caves that are likely completely protected from radiation. If we can go and explore in those caves… those caves may represent our best bet for places capable of supporting human colonies and supporting life that exists in the dark.

Fraser: And there's also been some orbital missions proposed that will map out the methane concentrations with more accuracy and try and even find out exactly where it's coming from.

Pamela: And everyone just wants to go dig… because who doesn't like digging in the dirt?

Fraser: Oh, for sure… but I mean this discovery… this could change everything.

Pamela: Yes.

Fraser: So if there's one mystery that we've really got to get to the bottom of… it is this one. But, let's move on… so, mystery number five–where did Titan's atmosphere come from? Titan is Saturn's largest moon… second largest moon in the solar system… and it has an atmosphere that is thick… like as thick as Earth's… and rich in hydrocarbons which scientists think is a very similar environment that we had here on Earth early on. How on Earth… ha, ha! How on Titan could you get an atmosphere like that so far out in the solar system orbiting Saturn? It should just be a block of ice, right? A ball of ice…

Pamela: Right, right… and this is where Titan gets to be a really interesting planet to look at.. it's not even a planet, it's a moon… it gets to be a really interesting object to look at from a geophysics perspective because it doesn't just have a thick atmosphere, but it has a "insert the expletive of your choice" thick atmosphere. This is atmosphere that is 1.5 atmospheric pressure–or atmospheric bars, rather. That's thicker than the atmosphere on the planet Earth.

Fraser: You could take off your spacesuit and not freeze-dry… you would merely freeze!

Pamela: And the thing about having an atmosphere this thick is… I love this… it's a low-gravity world. It's a tiny, tiny moon–compared to the size of the planet Earth–and so with this low gravity, if you attached a pair of Icarus' wings to your arms, you could actually fly around in this really thick atmosphere. Now, the majority of the atmosphere is nitrogen–it's 98.4% nitrogen. But, along with that nitrogen, there's another 1.6% composed of methane and other organics, and like I just said about Mars, methane is destroyed by the sun. So, somehow there's something about Titan that's causing it to constantly generate methane that's getting replenished in its atmosphere. People have looked to see… well, maybe it just captured the methane and it still hasn't had enough time to all be destroyed from the solar nebula. No, that model doesn't work. Well, maybe it just comes from getting clobbered by comets. No, that doesn't work either… the composition ratios are all wrong. Somehow, something inside Titan is generating this, and one of the really awesome things about the combination of Titan being really cold, really tiny, and having this carbon-atom rich environment, is it can have geophysical processes that carve rivers, that carve canals, that in many ways look just like the processes that we have with water here on Earth. So, for Titan, the methane in the atmosphere is like the water in the Earth's atmosphere. It can rain, it can form rivers on the surface, it can freeze, and so you can have an entire environmental cycle built out of methane… but we don't know where it's coming from.

Fraser: Right. So, methane is too short-lived to have been left over from the solar nebula, so some thing is either protecting or replenishing it on Titan.

Pamela: Exactly.

Fraser: Crazy. Alright, well I think we're actually out of time. We've gotten through five, and we've got more. So this is going to at least be a two-part series, so stay tuned for next week. Thanks Pamela!

Pamela: Sounds good Fraser.

Transcript: Solar System Movements

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Fraser: Even in ancient times astronomers realized there was something different about the planets–they move! The movement of the planets and their moons are governed by gravity, and as we all know, gravity can do some funny things. So, let's kind of go back to ancient history and sort of get an idea of what the ancient people thought… the way the universe worked.

Pamela: Well, originally it was all based on philosophy, looking up and imagining how the pieces fit together and, using philosophy, it was Aristotle who led the idea that all the planets orbited on perfect circles and the stars were embedded on a perfect sphere that embraced the planet Earth. And so it was all nested circles with the earth at the center moving outwards and outwards.

Fraser: And standing on the surface of the earth, that's the natural conclusion that you would come to. You look up into the sky and the stars seem to be moving and so it seems like the stars are moving around you, the sun is moving, the moon is moving, the planets are moving…

Pamela: And from one season to the next you don't see the stars move relative to one another, which is what you kind of expect if we were in a little tiny system where stars weren't that far away. Since the stars didn't seem to move, they just seemed to rotate around and around and around, it seemed natural… ok, they're just embedded on a flat… well they're embedded on the inside of a sphere that's not too big that embraces the planet
earth.

Fraser: Right. And how well were astronomers able to use this model to do astronomy?

Pamela: It made some predictions, but they weren't particularly accurate. You couldn't, for instance, using simply descriptions of… well, here's the sun on a circle, here's the moon on a circle, come up with a precise day and time for when an eclipse would be visible on the surface of the earth. You couldn't accurately say this planet was going to be right next to this star at this moment in time. So we had a theory, we just didn't have a way to back it up with evidence.

Fraser: Right. And then along came Copernicus.

Pamela: Well, Copernicus was one of the first ones to move that we should instead of having the earth at the center, have the sun at the center. Now this was again in part for philosophy and religious reasons. Unfortunately, his theory, while having at least the sun in the right place, it didn't do anything to really improve our ability to predict where things are located. And sadly at about the same time we had Ptolemy's theory with his earth-centered system and his epicycles that circles on circles trying to control the planets' positions… his theory was able to make much more accurate, but not completely accurate, predictions for where things would be located.

Fraser: Right. So Ptolemy's got these circles within circles, Copernicus's got just circles… but Ptolemy's math actually works out better?

Pamela: Right. Because he was able to correct for things by simply adding in extra cycles, adding in extra corrections, moving things around until everything worked out just right. He still wasn't able to make precise predictions, but he was better than Copernicus at being able to say where things would be at a given point in time.

Fraser: So when did the astronomy finally get accurate?

Pamela: Well, we finally figured out the math thanks to Kepler. He was working about the same time as Galileo–400 years ago. He was working with a man called Tycho Brahe who was the observationalist behind the team. Kepler was very much a theorist. So, Tycho Brahe had taken books and books and books worth of observational measurements of exactly where the planets were located. Kepler poured through these patterns looking for ways to mathematically match what had been seen on the sky. He tried all sorts of things… nesting circles mathematically within invisible geometric solids in the sky, and none of it worked. After a lot of mathematical head beating, he came to the realization that it's not circles that the planets are orbiting on, but instead… the ellipse. It's a slightly flattened circle in some cases, and by just making this minor change, by saying ellipses instead of circles, he was able to very accurately, within the ability of us to make measurements 400 years ago, he was able to finally predict where things would be located in the sky and when.

Fraser: And I guess part of the problem is that as a planet or some object's following an elliptical path around the sun, the speed that they're orbiting changes, so as they get very close to one of the nodes of this ellipse, they're going to go very fast, while when they're at the very far point of it, away from the sun, they're going to go slower. So, any time you're looking at the speed of the planet moving and trying to use that to predict where it's going to be, you have to know the shape of that ellipse or it doesn't do you any good.

Pamela: And for the planets that they were able to see back then–Mercury, Venus, Mars, Jupiter, and Saturn–they were very close to circles… with the exception of Mercury. It was just that slight difference that kept doing them in, mathematically, and he was able to overcome that slight difference. Now the problem is, the differences between Kepler's predictions, which only used the sun, even though he didn't quite know that at the time, differences between Kepler's predictions and reality slowly began to crop up. It wasn't until Newton came along that we were finally able to start understanding the differences and where they came from, thanks to understanding gravity.

Fraser: Right, apple dropping on his head… there's gravity.

Pamela: Right. And it turns out that you can use the exact same mathematics to understand that apple falling that you use to understand the moon falling around the planet earth.

Fraser: Now, I don't want any more mail about how that's probably never really happened.

Pamela: But the original documents describing how Newton told that story to one of his colleagues are now posted online and we'll try to link to them. So there is original documentation about this bit of gossip…

Fraser: Right. He saw an apple fall, yeah… so he said… but ok, please continue…

Pamela: Newton came along and he realized that it's forces that are controlling the motion, that the planet Earth… it gravitationally tugs on the moon and the moon tugs back. Our mass and the moon's mass, we orbit the sun and our planet is tugging on the moon, we're tugging on Venus, all the different bodies are gravitationally tugging on one another. And some of the variances we see in planets' behavior year after year after year, they're coming up from… well, Jupiter's giving Mars a good tug here and there, and Earth is giving Mars a good tug here and there, and together we're slowly evolving its obit, causing its orbit to change over time. In fact, all the planets' orbits are slowly changing over time.

Fraser: Ok, so let's then take a look at sort of the big picture here… all the planets orbit the sun…

Pamela: Yes.

Fraser: Why?

Pamela: The best way to imagine this is that all the planets are basically racing around the gravitational equivalent of a cyclodrome, where you have essentially a dimple in space-time. And if you have enough velocity racing around the inside of this bowl, you're just going to keep going in a circle. Now, not all of these bowls are perfect circles. The sun's gravity essentially creates a pit in space-time, and as long as the planets keep moving, they keep staying on the wall of this hole in the continuum. There's other descriptions where we mathematically start saying there's gravitons flying back and forth, and it's the gravitons that are communicating, "hey, there's gravity… you need to stay where you are." But the basic idea is the planets are trying to move in a perfectly straight line, and the gravity from the sun is going, "no… come to me." So as they try and go in a straight line, the constant yanking of the sun going "no… come to me" bends that straight line. So, they move a little bit forward, they move a little bit towards the sun… they move a little bit forward, they move a little bit toward the sun. And if any of you ever used the Logo computer language back in the '80s, this is how you draw a circle… you move forward… you turn. You move forward… you turn. And that's exactly how an orbit works.

Fraser: Right, and in this situation those forces are in perfect balance. If you made the sun more massive, the planets would all spiral inward and be destroyed. And if you made the sun less massive, the planets would all spiral outward into space and be lost forever. If you made the planets move any slower in their orbits, they would all spiral inward and be destroyed, and if you made the planets any faster they would all spiral outward. It's this exact, perfect balance. And that's leftover from the creation of the solar system way back when…

Pamela: It's not quite that deadly… if you varied something slightly, it would just move to a stable larger or smaller orbit. This is happening all the time because the sun is constantly losing mass due to its stellar wind, and at very miniscule levels the planets are slowly migrating away from the sun… and this is good! Because when the sun bloats itself up in a few billion years and leaves the main sequence, the earth will have migrated to a possibly safe distance away. But yeah, slight variations in any parameter cause the orbits to change.

Fraser: Alright, so let's take one planet, let's take a look at say Mercury, for example…

Pamela: Mercury, of course, is one of the completely…

Fraser: It's one of the more complicated ones, but sure… so then what way is it going around the sun… what direction…

Pamela: If you look down on the solar system in such a way that all the planets are moving in a clockwise direction, then this is said to be looking down on the north poles of every thing except for Venus which believes in standing on its head. So, looking down from the north at the solar system, Mercury appears to be going around and around and around in an anticlockwise direction. But its orbit is fairly elliptical. If you speak eccentricities, it has an eccentricity a little over 0.2 and this means you can actually see how flattened that circle is with your eye. On one side of its orbit it's a lot closer to the sun than on the other side of its orbit. And when it's closest to the sun, tidal forces… these are the same forces that cause us to always see the exact same side of the moon… tidal forces make it not want to rotate. So, during that period of time when it's closest to the sun, the sun pretty much stands still in the Mercurial sky. It's only as Mercury gets further and further away from the sun that it's able to orbit a little bit more freely. Luckily, it's moving really fast when it's close to the sun. It's moving really slowly when it's far away from the sun. So, the rate at which it rotates on its axis actually stays completely constant, it's just relative to where it is in its orbit, at that point when it's closest to the sun, the sun appears to completely stand still in the sky.

Fraser: So then if I could stand on the surface of Mercury and watch the sun, over the course of a day, or a year, what would I see?

Pamela: Well, you'd have to do a whole lot of waiting to see very much. A day on Mercury relative to its year is a fairly long, long thing to wait through. In fact, for every three times the planet experiences a day, it goes all the way around the sun twice. This is what's called a spin-orbit resonance. For the longest time, astronomers actually thought that Mercury was completely tidally locked. It's really hard to try to image the surface of Mercury from here, and it wasn't until the 1960s when we started imaging Mercury using radar that was sent from big radar dishes here on the planet that we realized oh… it is rotating, and realized over years… Mercury years… of watching it that it has this resonance in how long it takes to rotate and how long it takes to experience a year.

Fraser: And this is where I think we should distinguish between solar days and sidereal days…

Pamela: Right.

Fraser: A solar day is how long it takes the sun to return to the same position in the sky, while a sidereal day is how long would it take if you could look above the planet and not really think about the sun… how long does it take for it to turn back to the same spot. And here on earth, those are fairly similar… which we'll get to in a second, but on Mercury, they're totally different.

Pamela: They're totally different. And this is because we do have this strange rotation rate, where in order to get the sun geometrically in the same place in the sky, back to exactly noon straight overhead, you have to keep going and going and going around the sun, whereas well before you get the sun back in the same place, you've already gotten the stars back in the same place.

Fraser: Right. Now Venus… let's move on out, Venus is even weirder. I mean it's going around the sun in the same direction… all the planets in the same direction. They're all going in that counterclockwise direction, right?

Pamela: Right. Now the problem with Venus is when you look at… well where's its north pole? Its north pole, if you define the north pole as where your standing such that when you look at your feet everything is going around in an anticlockwise direction, its north pole is actually opposite of everything else in the solar system. In fact, when you look down, you see all the rest of the planets, happily you can see, for the most part–we have another problem when we get to Uranus–you can look down and see all their clouds going around in the same anticlockwise direction that they're orbiting around the sun. But with Venus, you look down and its clouds are going about in a clockwise direction as it orbits in that anticlockwise direction about the sun.

Fraser: Right. So imagine… look at the whole solar system from above, you're going to see all the planets all moving in the same direction… so Venus is obeying that rule. But yet, if you actually look at the planet itself, from the position of the stars, you would see it turning slowly backwards. And of course Venus is even more weird because a day on Venus is longer than its year… it's backwards day is longer than its year.

Pamela: Right. Yeah, so Venus is even weirder. First of all you have this upside-down motion, but then when you start looking at how long it takes for the sun and the stars to get back to where they started, well it's year… let's start with what it's year is. To get all the way around the sun is 224 earth days. And to an observer standing on the surface of Venus, you have the sun rising in the west and setting in the east, and from one noon to the next noon, that's going to be 116 days. So, that's most of the time that it takes you to get all the way around the sun. But because everything's going from west to east, the amount of time it takes to get the stars back in the same place that's actually going to be longer than an entire year. So, to get the stars back to where they started out at the beginning of the year takes 243 days. This is kind of weird and kind of special to Venus.

Fraser: Now I think we're fairly familiar and comfortable with our days here on Earth, right…

Pamela: I hope so…

Fraser: We've got the earth… well we say that a day takes 24 hours, and I think we've mentioned that that's a solar day. So it takes 24 hours for the sun to come back to the same place, while a sidereal day is shorter than that.

Pamela: Right, and that's to get the stars back to the exact same place they were in the sky.

Fraser: And that's actually the true rotational speed of the earth.

Pamela: Right. It's just not useful for when you're trying to make plans for the future because the stars vary a little bit too much from one point in the year to the next.

Fraser: Mars is similar to Earth, right… just a little over 24 hours. Jupiter has a crazy-fast rotation speed.

Pamela: Jupiter… it has an amazing speed of 9.9 hours to get the sun back to where it started. And then Saturn we don't know. Saturn's a bit problematic. Its atmosphere refuses to let us understand what's going on down in the center. We're trying to understand it using magnetic fields, but I'll just leave it at… we don't know.

Fraser: Right. We kind of approximately sorta think it's about 10 1/2 hours, but…

Pamela: We don't know.

Fraser: We don't know for sure…. because there's many ways to measure that. But I think, you know, the really interesting one is Uranus.

Pamela: Right. And this is the planet that apparently had a very bad life in the past. It's tilted completely on its side. And there's really only two ways to have a planet have that particular fate. One is that you just hit it with something about the size of the planet Earth, and if I were Uranus, I certainly wouldn't want to get hit with something the size of the planet Earth. And the other way is to be a victim of gravitational abuse from Saturn and Jupiter going through a weird resonance period during the early part of the solar system. We're not sure which one happened… it also could have been a combination of Uranus getting knocked about gravitationally by Saturn and Jupiter and getting hit by something smaller. We don't know. All we know is it's 97 degrees tilted over.

Fraser: Right. Which is essentially tilted over on its side.

Pamela: Right. So for all intents and purposes, its pole points at the sun when it has its winter solstice and when it has its summer solstice.

Fraser: Right. And this is where you sort of got to think about it. Imagine Uranus tilted over on its side, but it's not like it's rolling around the sun.

Pamela: No, it always keeps its pole pointed at the same set of stars.

Fraser: Right. So sometimes that pole has to go through the sun first to get to those stars, and other times the sun is on the opposite side of the planet, but still… Now, Pluto is not a planet anymore, but it used to have… I guess it still has a highly eccentric orbit.

Pamela: Right. And the thing is, though, we talk about it having a highly eccentric orbit, but its eccentricity isn't mathematically all that different from Mercury's. Mercury's eccentricity is 0.206 and Pluto's is 0.248, so those are pretty similar. The reason we notice Pluto's eccentricity is because its orbit cuts back and forth in front of Neptune. So sometimes Pluto is closer to the sun than Neptune is and sometimes Neptune is closer to the sun than Pluto is.

Fraser: And that difference in distance actually has a fairly interesting effect on Pluto which is that at its closest point it warms up to the point that its atmosphere pops up. Then when it's further away, its atmosphere freezes back down onto the surface.

Pamela: Right. So we have a planet that sometimes has an atmosphere and sometimes doesn't. This actually led Mario Livio to make a quote that I will forever love and that's "if you took Pluto and brought it in close to the sun it would turn into a comet, and that's no way for a planet to behave." So, what we're seeing is as Pluto gets closer to the sun it starts to "fuzz up" the same way a comet does as it gets closer and closer to the sun.

Fraser: It's exhibiting very comet-like behaviors. That's pretty funny. Ok, so now we've talked about the planets, and talked about how they're rotating… I want to talk a bit then… if we imagine the solar system as a flat… like a record… that is the plane of the ecliptic. And the planets are mostly orbiting on that, but not quite.

Pamela: Each of the planets' orbits is (relative to the earth's) a little bit tilted in one way or another. Exactly how much they're tilted varies. And for the most part, they aren't tilted very much. So we have for Mercury the orbital inclination–it's the most–it has a 7 degree tilt, Venus has about 3.4. All the rest are tilted less than 3 degrees. This is very slight and not the type of thing that's going to be very easy for you to get out and start measuring with your protractor.

Fraser: But this is why we don't see Venus pass in front of the sun…

Pamela: All the time…

Fraser: All the time… right. It's sometimes above the sun from our vantage point and sometimes it's below the sun.

Pamela: So the slight tilts that are out there do create a much less interesting observational universe. But what's neat is when we start looking out at the dwarf planets, at all the trans-Neptunian objects. They do have all sorts of different crazy tilts, where we see that Pluto is tilted 17 degrees and Himae is 28 degrees, so is Mak-mak, and Eros is 44 degrees tilted. We also start seeing the asteroids with tilts… where Ceres has an 11 degree tilt relative to the earth's orbit. So it's just the planets that seem to be locked in to this disk where we start looking at asteroids and comets and dwarf planets, these small-mass leftover bits in the solar system, they sort of end up on much more catawampus orbits around the sun.

Fraser: That is the first time you've used that word in this podcast, I think… catawampus…

Pamela: It's the best way to describe these objects…

Fraser: But still, if you were going to go look to discover new planets… this is Mike Brown's approach, the best place to look is on the plane of the ecliptic. That's where you're going to see them all. You're not going to look straight up above the solar system and see them, or down below. You're going to see them somewhere in that zone… helps you constrain your search.

Pamela: And every one of these objects crosses the ecliptic, so no matter what you're looking at, at some point it's going to be in the disk of the solar system.

Fraser: Now, what about the comets and the asteroids? I mean, the asteroids have kind of weirder… some weirder orbits and the comets can have really bizarre ones.

Pamela: The asteroids have a bunch of varied orbits, and for the most part they constrain themselves to being between Mars and Jupiter. But within all of these orbits we see occasional collisions… we think we just saw the remnants of one recently out in the asteroid belt. We also see asteroids that periodically decide that they're going to come in and start crossing our own Earth's orbit periodically. These are more of the Near Earth Objects. For the most part, yes… they do have more elliptical orbits but they're not ranging over the entire solar system the way comets do. Comets in many cases will start out in the Kuiper Belt, so they're starting out at a distance, in many cases, at a distance greater than Neptune's orbit, and then plunging all the way in… in some cases to plunge straight into the sun, but often to come in and dance between the orbits of Mercury and the sun or Venus or Earth and just coming right in to the inner part of the solar system and growing huge tails as they melt away in the heat.

Fraser: And when they're at their closest point, they're moving very quickly and then they slow back down. That's why we'll see them accelerate as they approach the sun and then slow back down as they're heading back out into deep space. They can go in orbits that last tens of thousands of years.

Pamela: And many of them will have, the one's that we're happy to keep observing over and over and over again, like Halley's comet, will have orbits that are measured in tens of years, but the period of time that they're in the inner solar system is a very small fraction.

Fraser: I guess the last thing to talk about is how the movement of the moons is governed as well by gravity.

Pamela: And again, we start seeing these interesting resonances, these interesting beat frequencies, when we start looking out at systems that have multiple moons. There're people that believe that the reason that Venus has such a really long day is it's in resonance with the planet Earth so that we're pretty much always seeing, when we're on closest approach, the same part of Venus. When we start getting out and looking at Jupiter's moons, we see different orbital resonances that keep its moons coming in so that they line up the same way every few orbits. We see this in particular with Io and Europa which are both being tidally heated leading to, on Europa, liquid water beneath its surface and on Io, massive amounts of volcanism.

Fraser: There's a resonance between those two moons, so every time Io goes around Jupiter twice for every time Europa goes around once?

Pamela: There's actually a really neat 1 to 2 to 4 resonance between Jupiter's moons Ganymede, Europa, and Io, leading to Ganymede goes around once for every 2 times Europa goes around for every 4 times Io goes around. We also see a 2 to 3 resonance with Pluto and Neptune. Resonances like this happen all over the solar system. And what's great is we can see the exact same mathematics applied to Jupiter and its moons that we see with the planets. This was one of the things that really made it clear that Kepler's physics and Newton's physics were right was we had Galileo looking at Jupiter's moons at the same–relatively, in the grand scheme of human history–that Kepler was coming up with his orbital mathematic equations… Kepler's three laws. Scientists in the following decades were able to say, oh… this applies to Jupiter as well. So we can look out and we can apply the same mathematics to Jupiter, we can see it at Saturn, we can see it orbiting all of the planets. We know that these gravitational tugs tend to lead to things ending up in resonant orbits.

Fraser: Of course, that story is going on at even larger scales with the movements of the galaxies and the interactions of the galaxies in the whole large-scale structure of the universe. But that's another story… that we've already told, I think. Alright, well thanks a lot, Pamela.

Pamela: It's been my pleasure, Fraser.

Fraser: Talk to you again…

Pamela: Bye bye.

Transcript: Coordinate Systems

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Fraser: 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. Hello Pamela.

Pamela: Hey Fraser, how's it going?

Fraser: Good. So I've got to admit, this is a show for me today. This is my show…now the rest of you can listen in if you want, but this is sort of designed to help me get over a bit of a mental block that I've got, so yeah… so this is going to be one of those weeks where we tackle something you're mentally avoiding, and by "you" I mean "me." You all know those astronomical terms like alt-azimuth, right ascension, declination, arc seconds, arc minutes… of course not, your mind has blocked them out. But today we're going to explain them so you don't need to avoid them anymore. Soon you'll be ready to find anything in the cosmos. I will readily admit that if you give me the alt-azimuth numbers or the right ascension and declination and say go find that thing with your telescope, I will just give you a blank stare. If you say, "Show me how big something is in arc minutes," I would just kind of draw a circle and show you and kind of hope I was right. So, yeah, I… I know the moon is half a degree across, I've used that in enough articles now that I know that, but honestly…. so I just have this mental block and I just pass right past it. So today, we go with my mental block and maybe everybody else's as well so–coordinate systems, so Pamela what are the different coordinate systems that astronomers use to find something in the sky?

Pamela: There's basically three different coordinate systems that we use most. The first is the one that you learn when you're learning how to use an amateur telescope and that is the "altitude-azimuth" or "alt-az" system which just tells you where something is relative to the horizon. Then there's the equatorial system. This is the system that is used on almost all star charts. But sometimes when you start looking at the galaxy and start looking at the universe as a whole you want to go out and start using galactic coordinate systems instead. So those are the three primary ones in use. But if you start dealing with historic documents, you pull in a fourth coordinate system which is the ecliptic coordinate system.

Fraser: Right, and that's still used in astrology… but you know…

Pamela: Yeah. The rest of us, we just noted it for historical reasons.

Fraser: Right. Ok, well let's just start at the beginning then. So, I get a new telescope, I'm going to learn the altitude-azimuth method. How does this work? What is this based on?

Pamela: Well, quite simply, the altitude is how many degrees above the horizon is something located, and you're hoping it's a lot of degrees above the horizon because if you're down near the horizon you get lost in the atmospheric muck.

Fraser: Ok, so horizon to directly overhead…

Pamela: Which is the zenith point….

Fraser: Which is the zenith point–how many degrees is that?

Pamela: That's 90 degrees.

Fraser: 90 degrees, so there would be like 90 lines from the horizon up to the zenith point. Ok, and are they equally spaced? So…

Pamela: Everything's equally spaced, and the way we actually look at it isn't lines it's how many fists above the horizon is something.

Fraser: This is fist held at arm's length.

Pamela: Fist held at arm's length is about ten degrees. So you can fit nine fists, if you do it carefully and accurately, between the horizon and straight overhead.

Fraser: Right.

Pamela: And this works for little people and big people because the bigger your hand is, the longer your arm should be. So that big hand ends up far away from your eye and it still looks like it spans ten degrees. And a little hand is usually attached to a little arm putting it closer to the eye, making it still cover up ten degrees.

Fraser: Ok, and so then how will that be sort of described… so if I'm going to see the altitude measured, to go look for it, will it say like it's ten degrees above the horizon? How will they mark it?

Pamela: Right, so that's actually–most times when you're looking up coordinates, unless you're looking up…. yeah I can't think of a time that you're looking something up that they say "alt-az," but when you're setting your telescope up you start to worry about these things so the north pole, for instance, the north pole is zero degrees azimuth, and then where that north pole star is located, assuming you're in the northern hemisphere, is going to depend on what your latitude is. So if you're at zero degrees, if you're right on the equator, then the north pole is zero degrees above the horizon. If you're 30 degrees north of the equator, then the pole is 30 degrees above the horizon. So it has an altitude of 30 degrees.

Fraser: Right. Ok, and if you're standing on the north pole…

Pamela: If you're standing on the north pole, it's straight overhead so you're 90 degrees north of the equator, and in turn the north pole star is 90 degrees above your horizon.

Fraser: Ok, alright, and then you started to jump to the next part of it which is the azimuth.

Pamela: Right, and so the azimuth, that tells you where in the sky something is located around the clock dial, essentially. So if north is noon, and as you work your way off that angle, you can say you're going 30 degrees east, and so when you go 30 degrees east you basically follow in a clockwise direction around the horizon. You can say that something is 40 degrees west and go in an anticlockwise direction around the horizon.

Fraser: Ok, I got that. So if you tell me to go to look 90 degrees east, I will sort of stare at the north pole, at the north star, and then I will turn to the right 90 degrees.

Pamela: And you'll end up looking dead east at that point.

Fraser: I'll be looking dead east and that's the direction I'm going to be looking at. Ok, so then to sort of put that all together then, are there minuses, plusses, how would you put it all together into numbers so I could kind of break it apart? So if you gave me a altitude-azimuth coordinate, what would it look like?

Pamela: It would be something like 45 degrees altitude, 30 degrees east.

Fraser: And is it always going to be 30 degrees east, or would it just say 30 or…

Pamela: It will give you an east or west direction.

Fraser: So if it's west, then I'm turning left from looking at the north star.

Pamela: Yes.

Fraser: Ok, alright, so I think I've got that. Now what if… I guess you can't see below the horizon so it's always going to be… things are always going to be from the horizon and up.

Pamela: Yes.

Fraser: And so I'm going to use my fists or sometimes use fingers, I know Tammy, one of the writers on Universe Today, she goes, "use this many fingers up, so one fist and two more fingers."

Pamela: Right. So your three middle fingers are about four degrees, the tip of your little finger is about one degree, and this allows you to find your way around the sky fairly well.

Fraser: Right. And if you're going to have to turn 45, just go half-way between north and east, and if your going to have to turn… right, so I think I've got that.

Pamela: So the only time you'll actually see alt-az written down is when it's associated with a time. So you might see, if you go outside at 10 PM tonight there'll be an iridium flare 40 degrees above the horizon at an azimuth of 25 west.

Fraser: Now, what is the advantage, why do they use this one compared to other systems?

Pamela: Because it's the simplest way to build a telescope. That's really all there is to it. In order to use the other types of coordinate systems, you have to take into account the tilt of the pole, and so you have to put a wedge on your telescope, you have to essentially take into account the fact that our planet's rotated in figuring out where things are located in the sky. So alt-az has problems insofar as, well the sky is moving. But given a specific time and a specific place on the planet and a telescope that doesn't have a wedge, you're stuck in an alt-az coordinate system.

Fraser: Right. So that would be like a big Dobsonian, or something… so will the telescope actually have the degree…. have that built somehow onto the mount?

Pamela: Right. That's the problem is the mount itself, unless you have a wedge, will only tell you your altitude above the horizon and your azimuth, assuming you bothered to line it up with north.

Fraser: Right.

Pamela: So your telescope leaves you kinda stuck.

Fraser: Right. But if you, you know, you can get pretty close, right? Your telescope, your mount is going to show you what your altitude is, it's going to show you what your facing is, assuming as you said that you start, that you line up north with north, and then you can turn your telescope around and it will sort of tell you what your facing is, and then as well up and down, what your altitude is.

Pamela: Right. Now, the only problem is that when you look up coordinates, in general, they're always given in something else. So, your telescope is giving you alt-az coordinates, and then you need software or something to translate to more universal coordinates that don't care what time it is, that don't care where on the planet you are, and this is where we start to get to the equatorial coordinate system.

Fraser: Hit me! I'm ready!

Pamela: So, the equatorial coordinate system is defined by essentially taking key points on the planet Earth and extending them out to the sky. So, we take the planet's equator and we expand it out and turn it into the celestial equator. We take the north pole of the planet and spit it out into the sky and make it the north pole of the celestial sphere. Here, instead of having latitude and longitude, we have what we call declination and right ascension. And declination, well that's our north-south way of measuring things. So the equator is again zero, the north pole is 90 degrees, south pole is minus 90 degrees. And then the right ascension is designed to confuse. Basically, they sat back and they said, "Ok we need to define a zero point on the sky, somehow." But the sky is moving. So how do we determine what zero is? And what they came up with is the zero point is the point on the sky that is exactly lined up between the earth and the sun on the vernal equinox. So, if you want to find zero, you wait until the vernal equinox, draw a line through the sun and notice that you can't see because the sun's in the way. So then you wait six months and on the autumnal equinox you wait and you see what is exactly overhead at midnight. And the actual definition says "at midnight at Greenwich England on the 0th meridian line" as well.

Fraser: And is that the same spot every year?

Pamela: And this is where precession comes in.

Fraser: Ahh…

Pamela: So, it's not actually the same point every year. The north pole of the planet Earth is constantly changing.

Fraser: Right, it's wobbling.

Pamela: Right. It's both precessing and it's also going through a process called nutation… it's wobbling. And so the exact zero point of the RA system changes every single year. So when you look up coordinates in a book, the book will always tell you, well these are the coordinates for 1950, these are the coordinates for the year 2000. Pretty soon we're going to need to come up with a new set of coordinates because as it turns out, in just a 50 year period, an object can move about 7/10 of a degree which, in the grand scheme of things, doesn't seem like that much, but when you're trying to point a telescope, that's a huge amount. That's enough that you can start worrying about, well am I picking up a planet, am I picking up its binary companion, am I picking up the correct galaxy in a cluster? So, again computers get in the way, save us from having to do the calculations, take coordinates that we look up that are 1950 coordinates, 2000 coordinates and translate them into whatever year the observations are being made.

Fraser: So then if I'm standing on the equator, my directly overhead then is going to be half-way between the north and south pole, right?

Pamela: So directly overhead you have zero degrees declination.

Fraser: Right. OK. And if I'm standing on the north pole I have 90, and if I'm standing on the south pole I have minus 90?

Pamela: Directly overhead.

Fraser: Right. Ok, alright. And then you mentioned that it's at the point where the autumnal equinox or the vernal… so whereabouts is that in the sky?

Pamela: So, it actually coordinates quite nicely for being the first point in the constellation Ares. So if you find the constellation Ares, its westernmost point is going to be the 0th point, and then as the sky rotates, as you move east across the constellation, you get to higher and higher right ascensions.

Fraser: Right, and I'm thinking of Ares right now. It's like… I think of it as three stars. There's like two long ones separated and then a little one that jigs down.

Pamela: So you know your constellations you just don't know where they're located.

Fraser: Right… right. Well, like I know where they are sort of in relation… I go out and go there's, you know… it's, it's March, or sorry, it's um you know April, May, you know… there's–I don't know–Andromeda, right… you know, it's winter and there's, there's Orion, but…

Pamela: So, it's basically a V with a tail on it is the way I think of it.

Fraser: Yeah, right. So, you can, so it's sort of the beginning, the westernmost side of that constellation is the 0th point. And then, so then which way, right? So if I'm looking at Ares, which way is positive and which way is negative? Or is it just one number?

Pamela: Well, it never goes negative, it goes from 0 to 24, it's actually measured in hours with right ascension.

Fraser: Ah, well that makes sense.

Pamela: So, if you go outside on the fall equinox and you look straight up at midnight, what you should be seeing is the first point of Ares. And then as you watch the clock change, and as you watch the sky rotate, one hour later, one hour of RA will be straight overhead, two hours later, two hours of RA will be straight overhead. So as the sky rotates, you see increasing hours of right ascension pass overhead.

Fraser: Right, ok I see, so it really takes into account the rotation of the earth which makes the stars seem to move.

Pamela: Yes.

Fraser: Right, ok, and so that's how I can… because that point in Ares is always moving in the sky, I just find that point in Ares and then I can just measure off of that one way or the other.

Pamela: Yes.

Fraser: And then I can go up and down, following from the north pole to the south pole, following the celestial coordinate. Ok, that almost makes sense. So then how will numbers in declination and right ascension be expressed?

Pamela: They're always expressed as, well ok, Sloan Digital Sky Survey changed how they're always expressed. Up until Sloan came along, it was always right ascension in hours. So you'd see something that was 16 hours 32 minutes 24 seconds. And then declination was typically done in degrees minutes seconds but sometimes decimals cropped in because people got tired of converting between hours, minutes, seconds, and Excel likes to use decimal degrees instead. So declination would typically be something between 0 and 90 or 0 and negative 90 degrees minutes seconds.

Fraser: Ok, alright, so then I'd know if it was 16, then I'd know that I would turn 16 hours worth of motion from the point of Ares to the left until I saw it, is that right? No, to the..

Pamela: To the east.

Fraser: To the east, so I'd turn right, so I… so if it's, you know, it it's one hour, then I'd turn 1/24 of the sky and look to the east.

Pamela: Right, and if it's 16, you look between your feet, basically…

Fraser: Depending on where you are.

Pamela: Depending on where you are. If you're looking at a circumpolar object, you could be looking down from the north pole for instance.

Fraser: Right. Ok, alright. So that gives us sort of our second system. And now let's add the third system on.

Pamela: Well, this is the galactic coordinate system, this is where we start using our galaxy to define its own, well our galaxy has an equator, our galaxy has a north pole, our galaxy has a south pole, so let's use those to define the coordinate system. Now, the tricky bit on the galactic coordinate system is, well, we can't get to 0,0. That's, if you think of the way a nice friendly coordinate system would be, the very center of the galaxy would be the center of the galactic coordinate system. But, on the sky, that would lead to a lot of confusion, because then you have to do all sorts of corrections for the earth's position and it just gets ugly very quickly. So the way we actually define the coordinate system is here we are, planet Earth, except then we imagine we're actually at the sun, because the earth moves around the sun…

Fraser: Here we are Sun, center of the universe…

Pamela: Right. And then we draw a line from the sun to the center of the galaxy. And that line that we've just drawn, that line defines where our 0 degrees galactic east-westish type coordinate systems are. So we have a circle going around the plane of the galaxy pointing from the sun straight through the center out the other side of the galaxy gives us 0.

Fraser: Right.

Pamela: Now if you go 90 degrees in a clockwise direction that gets you to 270 degrees. If you instead go 90 degrees in a counterclockwise direction, that gives you 90 degrees, and these are your galactic longitudes.

Fraser: And so then how would we measure an object? Right…once again, using the galactic coordinate system, I want to find Orion nebula, how would I do that?

Pamela: So, you need another coordinate as well, you need to know the latitude, and this is how many degrees up from this plane of the galaxy an object's located, so if you look out you might say that you're looking 27 degrees longitude, but then you also need the latitude which tells you how far out of the plane an object is. That will again go, if you're pointing towards the north galactic pole it will go from zero to 90 degrees, if you're looking down through the galaxy towards the south galactic pole or past the south galactic pole as the case may be, that gets you to minus 90 degrees.

Fraser: But isn't that kind of the same as the declination right ascension just different center points?

Pamela: It's exactly the same but has different center points. We're going from using the plane of the planets, as defining where the equator is. Actually we use the equator of the planet earth, not the orbital plane, but they're close.

Fraser: But we don't have… you know when I think of the galactic coordinate system I imagine, you know, the way that in Star Trek they would navigate around the galaxy. But there isn't really anything that works that way, there's nothing where you say, you know it's in this direction and it's 42 light years away.

Pamela: No. Because when you're just trying to find something on the sky, that's not useful.

Fraser: Because this is all just… from our perspective the entire sky is just a sphere that we look at and find points on that sphere. We don't care how far things away are. That kind of navigation is irrelevant. So, to think of an analogy, can you imagine if ground-based navigation worked the same way? So from my perspective here in Vancouver, right, Calgary and New York City are very close to each other. And London is just… London is also very close.

Pamela: But we actually do exactly the same thing in some ways, because we ignore up and down relative to the surface of the planet, so when I tell you where something on the planet is located, I give you a latitude and longitude position, but that means that an ocean liner, which is on the surface of the ocean, an airplane, which is above the surface of the ocean, and a submarine all have the exact same latitude and longitude position.

Fraser: Right. But they could be several kilometers apart.

Pamela: So, here what we're dealing with is that when we look out on the sky, that's a single skin that we're essentially looking at, but as we look at things superimposed on that skin you might end up with the random lucky alignment where you have Saturn, some star, and some distant galaxy all roughly superimposed in the same field of view on your telescope.

Fraser: Right. Even though they're obviously very far apart. Ok, and there isn't any universal coordinate system which accounts for the distances of things and lets you navigate your starship to them?

Pamela: Well, this is where we bring in to account things like red shift. So, when I'm building visualizations to fly through the universe I include latitude and longitude position on the sky or the RA and dec position on the sky, but then I give the red shift information as well, correcting it, as needed, for motions inside of clusters, and stuff. And it's that red shift that gives me that third dimension.

Fraser: Right. And that tells you how far away things are because how fast they are moving away from us. That's cool.

Pamela: Exactly.

Fraser: Ok, now there's sort of one last piece of the puzzle here which is the degrees, arc minutes, arc seconds and fractions thereof, and often, I know things will be like measured… you'll see a photo from the Hubble Space Telescope and they'll say that this planet measures one arc second across, or something like that, right?

Pamela: Right.

Fraser: So, then what are they talking about?

Pamela: Well, that's the perceived size on the sky. And we use time because… well it used to be the easiest way to measure position was you built a very stable building and you built a cross-hair, and then you looked at the cross-hair, and time is fairly easy to measure, and so you measured the time at which something crossed the cross-hair on one side and the time that the other edge of it crossed the cross-hair. That could tell you, for instance, how big the Pleiades were as they passed through your cross-hairs. What it boils down to is one hour is the size… it's 15 degrees across. It's the size of something that takes one hour to pass straight overhead. One minute is 1/60 of that, it's something that would take 60 seconds to pass overhead.

Fraser: Right, so just for some comparison, right, so let's say we have the moon, and I know that the moon is 1/2 a degree across, so how long then does… I'm doing some math in my head here, how long does the moon take…

Pamela: Well, this is where things get kinda tricky because we have 2 different… we have arc seconds in time and then we also have in degrees. So, RA is a measure of time. Declination is in degrees, just to confuse you…

Fraser: Is there a translation?

Pamela: Well if you take the entire sky, there's 360 degrees all the way around the sky, there's 24 hours all the way around the sky, so there's 15 degrees is equal to one hour.

Fraser: One arc hour.

Pamela: Yes.

Fraser: And then we can start dividing it up by then.

Pamela: Yes, so if I have one minute of RA that's going to be how something crosses the sky. Now if I say it's ten degrees across, that's my fist held at arm's length. If I say it's one degree across, that's my pinky held out at arm's length. And if I say one arc second, on the degrees system, that's I yank a piece of hair out of my head and hold it out at arm's length and the width of that piece of hair is one arc second.

Fraser: Right. And we have a difficult time seeing one arc second. How small of an object can the human eye perceive?

Pamela: That depends on the human eye.

Fraser: You know…

Pamela: The real problem is more of our atmosphere. The atmosphere is typically only good to 1 to 3 arc seconds, depending on where you are on the planet, and the human eye can usually get down to 1 or 2 arc seconds fairly well. But below that you start to run into confusion between the sky and what the eye is capable of.

Fraser: And so when we get, like, Jupiter… I'm not sure if you know how big it is offhand…

Pamela: No, I have to admit I don't…

Fraser: But, you know, we can't resolve Jupiter as a sphere or as a circle with the naked eye.

Pamela: Actually, some people can…

Fraser: Those people are liars. I kid…

Pamela: So, when Mars was at its closest approach a few years ago, it was 3 arc seconds across, and that starts to be at the point where if you have really good eyes and really perfect skies, you can look up and say, "Oh, that thing isn't behaving the way other things are behaving… that's a disc.

Fraser: You get that a bit with Venus, I find.

Pamela: Yeah, and with Jupiter, the whole system with the planets and everything, you're starting to get to the point where people with really good eyes can start to separate the moons away from the surface of Jupiter. So, looking out at the different planets, Jupiter can be 30, 40 arc seconds across… that is a clear, apparent disc. Saturn's 15-20 arc seconds across ignoring the rings. That again is something you can see as a disc.

Fraser: But is it just that the glare makes it hard to see it, or something?

Pamela: Well, the human eye isn't really good at telling area is what we're actually running into. And this is where you get to the "Twinkle Twinkle Little Star" nursery rhyme being how you differentiate between stars and planets. Stars are point sources, they have a single beam of light coming at us and the atmosphere tends to make that jumble around a lot more than a disc of a planet. So, with normal skies, planets don't twinkle, stars do. Now if you have really, really bad skies, then everything's twinkling. But in general that nursery rhyme helps you differentiate the stars from the planets.

Fraser: That is cool. Well, I think we uh… I think I now finally understand it. And for about the next hour or so, I think I'll be able to keep it in my head and then it'll be gone… that's alright. But thank you very much Pamela, I do appreciate that. You know a lot of the shows you know I sometimes know more than I perhaps lead off, but this episode–all new to me. So that's great.

Pamela: Cool.

Fraser: Alright well thanks a lot!

Pamela: Bye bye.