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Transcript: The Oort Cloud

Fraser: Astronomy Cast episode 292 for Monday, February 4, 2013 – The Oort Cloud

Fraser: 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.

Fraser: My name is Fraser Cain, I’m the publisher of Universe Today. With me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville and the director of cosmoquest.org. Hi Pamela, how are you doing?

Pamela: I’m doing well Fraser how are you doing?

Fraser: Great. I’m not sure if anyone is going to get this but we are going to be at South by Southwest in Austin for the South by Southwest interactive exhibit with NASA. We’re going to be near the great big model of the James Wood space telescope from March 8th to March 10th and so if you’re going to be in Austin, by all means come by and say hi to us.

Pamela: We aren’t going to be doing a meet-up because our meet-up is the NASA tent so come join us. There is no bracelet required and is open and free to everyone.

Fraser: We’ll be there for three straight days so by all means come by, say hi and shake our hands.

Fraser: In the very outer reaches of the Solar System is a region of space known as the Oort Cloud, which may extend as far as a light-year from the Sun. We only know about the Oort Cloud because that’s where long-period comets come from, randomly falling into the inner Solar System from time to time. So Pamela this is a funny thing where we have an object, a structure, a thing in space that we actually have never seen right? We have to presume that it’s there but we actually can’t see it.

Pamela: It’s really annoying because there are so many different things that it might be effecting. There are people that hypothesize that this continuous shell of icy material and dust around our solar system creates reddening. There are people that say that it’s impacting our ability to measure distances and perhaps it’s impacting how we observe the cosmic microwave background. We don’t know. There are all of these things that it’s presence may or may not be effecting and that’s kinda really super annoying.

Fraser: I had no idea, that’s really interesting. You can imagine that depending on what the composition of the Oort cloud, which we’ll explain in a second but now I’m just excited thinking about this; it’s actually distorting our view of the cosmos because it’s this bubble that could be this bubble around us. So for anyone who doesn’t know lets go back again and actually talk about what an Oort cloud is.

Pamela: It’s basically this two component glob of stuff. To get scientific,

Fraser: That was very scientific.

Pamela: (Laughs) There is considered to be, for the Oort cloud, two components. One is the big sphere that everyone talks about that is roughly a light year across. .8 lights years, to be more accurate, is it’s theoretical outer limit based on how far away something can be and still be gravitationally attached to our solar system. It’s considered to be the source of some of our longest-period comets and the things out in it are considered to be building in small moon-sized chunks of ice. Because we can’t observe these suckers, we really don’t know what their limitations are. This could be just a big brother to Kuiper Belt, in which case, we have a bunch more of these dwarf planets out there; it could be limited to smaller objects, we don’t know. Nested inside this big spheroid of material is what’s called the hill zone. These are a disc light component to the Oort cloud.

Fraser:  So where does the Oort cloud come from?

Pamela: Well it actually came from a variety of different places depending on who and which theories that you adopt. Most likely it came from a combination of places during the formation of our solar system. The outer part of our solar system was mingling with the outer parts of other solar systems and we stole what we could gravitationally; some of the constituency of the Oort cloud is probably stolen material from other solar systems.

Fraser: If it’s this cloud a light-year or .8 of a light-year across, that’s a pretty big bubble that surrounds the solar system. You could imagine these star systems’ Oort clouds passing through each other and material jumping ship from one place to another.

Pamela: Yeah and one of the more intriguing things is that we probably have some stolen material and occasionally this stolen material gets gravitationally bumped until it comes into our inner solar system where potentially we can sample it.

Fraser: I know that when we do meteorite samples in the solar system we find that all of the meteorites tend to have the exact same formation date. They all formed 4.6 million years ago with the formation of the earth and the sun but can you imagine if we found a sample of one of these comets that had a different age?

Pamela: It’s harder to do that with ice because you’re dealing with ammonia, frozen methane, carbon dioxide, carbon monoxide and all these frozen gasses. It does get more difficult to age date them but you can look at the compositional radius and say the composition of this object doesn’t match anything else we’ve seen. The issue is that comets have a huge variety so we’re still trying to figure out what exactly is within a normal boundary parameter for a comet. The more we explore the Kuiper Belt the more we’ll understand what something that formed with our solar system should look like. In the future as we look at these long period comets coming into our solar system, hopefully we’ll be able to say which ones are natives and which ones are the explorers of other solar systems.

Fraser: So we stole material from other solar systems…

Pamela: That’s part of the source of the Oort cloud

Fraser: Right… Maybe… Probably… Who knows?

Pamela: The rest likely came from, what can best be described as, the angry dance of Saturn, Jupiter, Uranus, and Neptune in the early days of the solar system. As Jupiter and Saturn passed through, having resonate orbits, they basically flung material in all directions. Some of the material, roughly a quarter of it, got flung into the inner solar system and roughly a quarter of it got flung into the outer solar system entirely. Probably about half of this material ended up getting sent into extremely elliptical orbits; orbits that will mirror what we see for the long-period comets. Because of the nature of the interactions once that stuff gets out there the material does spend the bulk of its time in it’s most distant points in its orbit. This is true of every orbiting object. It’s the Kepler equal area and equal time law where when you’re in close you sweep out this very fast angle so you can sweep out an equal area to the amount that you… when you’re further out, sweep out and in the same amount of time you move much much slower. Now once the objects are out there they have the potential to gravitationally interact with other stars, with dark molecular clouds and with all these different things that we see as our solar system passes through the galaxy. All of these different interactions, even an Oort belt object on Oort belt object interaction, can work to smooth out the orbits to make them more and more spherical and more and more and more circular over time to create this distributed spheroid material.

Fraser: I guess that was leading into my question which is that if there is these interactions of the giant planets in our solar system kicking all of these objects out into the outer solar system, you would think they would all be on these parabolic orbits where they are going out and are all going to come back in and keep doing orbits like the comets do. I can see that once they get out there they have interactions and maybe interactions with other stars and it changes their orbits and free body interactions and eventually you get whatever remained is a cloud and everything else was gobbled up by the sun.

Pamela: The things that are on parabolic and hyperbolic orbits might pass through the inner solar system once and then they’re gone. It’s the elliptical ones: some of them remain as comets, some of them did have circular orbits and then got disrupted again and became comets but most of them the orbits relax over time and then we end up with this nice spherical component. We theorize it seems to match all of the comets that we see coming in; they have to come from somewhere but we don’t have certainty.

Fraser: So we’ve got an idea of maybe the source of this cloud, what about the discovery and the name? Where did that come from?

Pamela: The name comes from the person who finally got the theory listened into. This is one of those horrible examples of science that things get named after who has the most loud way of presenting the information. Back in 1932 Estonian astronomer Ernst Opik… I think I pronounced that one correctly, theorized that all of these long period comets that are coming at us from all different directions. Unlike most of the things that we see in our solar system, their orbits aren’t confined to the plane of our solar system. They don’t come from the same place that we see asteroids coming from rather they’re coming from all different directions, completely randomized. The only way to get to this completely randomized origins is if you have an orbiting cloud at the outer-most edge of our solar system. He put forward this theory and then in the 1950′s it was re-theorized a second time or rediscovered if you will by Jan Hendrik Oort. It was a way to try and understand where all of these comets are coming from and trying to understand why all of these comets that we see have such unstable orbits. When you see these sun grazers or when you see these clearly parabolic and hyperbolic orbits, which means they come in once and then are gone forever, those clearly aren’t things like the planets which are orbiting over and over and over. Where are they coming from that they can keep getting renewed? The only way to solve this paradox was to create a reservoir of comet material in our outer solar system so later in the 1950′s Oort made this postulation. Let’s face it, the word Oort is much more fun to say than Opik. Oort ended up getting to have his name associated with this cloud of material in the outer solar system.

Fraser: So what about the Hills cloud then?

Pamela: That again is a theorist came along worked on postulating how to explain all of the distribution of material and since it’s a mostly random but not entirely random distribution where there is this preference towards things being in the plane. That preference can get explained by a second component that overloads the plane of the Oort cloud.

Fraser: Is it one of those situations where there are extra comets coming from that region and then that would be explained by this gravitational…

Pamela: …Second component.

Fraser: Yeah, to give you this hills cloud. Again this is pretty tricky right because there is no observable evidence for this cloud at all.

Pamela: The way to think of it is if you’re getting sprayed with water you know there is going to be either a cloud or a hose involved. Depending on how you’re getting sprayed with water you can start to figure out what characteristics the source of the water must have. Here we’re seeing the outcome, the water falling on us so we have to put together the pieces of what must be some of the characteristics. If you can detail how far away the water is coming from you start to be able to place boundary conditions. The comets are the frozen water that is falling on us that places the boundary conditions on the physics that helps us describe this unseen frozen water faucet in the sky.

Fraser: Lets talk about the comets that are coming out of the Oort cloud because that is what we do have direct experience with. What kinds of comets do we get from this cloud?

Pamela: Well for the most part they are long period comets; things like hail bop that have orbits that are measured not in lifetimes but in generations or in the rise and fall of empires. These are thousand year periods in some cases. We also get a few interesting exceptions like Haley’s comet which through interactions that it had with Jupiter in the past, at least we thought it was Jupiter, it’s orbit got changed so that it’s now a shorter period comet but its crazy orientation indicates that it’s not one of the ones that originated in the Kuiper belt.

Fraser: The Kuiper belt object, where are we going to be looking at? What kind of period? These are the short period comets and they are measured in dozens of years.

Pamela: There’s tens of years, hundred years-ish, it’s that order of magnitude but with the long period comets you’re looking at thousands of years.

Fraser: Thousands and hundreds of thousands. So every comet is completely unique. The first time you see one of these long period comets you’re never going to see it again.

Pamela: That’s one of the frustrations and one of the other frustrations is even the Oort cloud objects that begin to dip their way into our solar system; they have such extremely long orbits that they may not spend very much time in an observable part of our solar system. A lot of scientists think that the dwarf planet Sedna is about roughly 1500 km across. It comes into just 75 astronomical units from the sun and that’s an extremely large distance. Compare that to the 35 to 45 of most of the objects that we’re looking at. That’s its nearest approach.

Fraser: And then it goes out to…?

Pamela: It goes out to 1000 astronomical units

Fraser: Yeah and takes 10,000 years or something like that to do it’s orbit. It’s crazy.

Pamela: We have other objects with less beautiful names like 2006SQ372. It’s a 100 km-across object and we were able to find it because it came all the way in to about 25 astronomical units so that’s inside the orbits of the outer-most planets and then it will go out to about 2000 astronomical units.

Fraser: By any other name these would be comets. If they got closer in to the sun they would…

Pamela: …but so would Pluto.

Fraser: So would Pluto, true. So would Enceladus. They would grow a tail and could you imagine if Sedna or one of these got within Mercury’s distance or Venus’ distance of the sun it would grow a tail. It would be unbelievable. Most comets are only, what, 10-20 km right? They’re small?

Pamela: Yeah

Fraser: So these would be the brightest objects ever seen, it would be unbelievable.

Pamela: That would be kind of cool.

Fraser: Wouldn’t it??

Pamela: Unfortunately the bigger an object is the more force is required to disrupt its orbit. The likelihood the big ones are going to get jostled enough to come in and pay us a visit is fairly low. Luckily the small ones are fairly easy to jostle.

Fraser: But the small ones are also very dangerous.

Pamela: Yes, Tunguska experienced that back in the early 1900′s out over Siberia where roughly 1000 square miles of trees got damaged and/or flattened. Windows shook for thousands of miles;  it was a big event. We try to avoid getting too close to comets but they’re not something we can move our planet out of the way of.

Fraser: Yeah we’ve talked about this a bit in past shows. With an asteroid you can predict 100 years in advance that it’s in a dangerous orbit and you can take that time to research it and study and move a space craft out and try to use a gravity tractor, paint it, shoot it with nukes or whatever you’re going to do, you’ve got time. Even with the short period comets you’ve got time but with the long period comets you’ve got months and then POW.

Pamela: If that. One of the unfortunate things is that because they do have such highly elliptical orbits you basically are making a nice edge pass through the solar system. Depending on unfortunate geometric circumstances it could be that something comes in from behind the sun that we don’t notice until it’s making a pass, basically out of the part of the sky that the sun is located in, straight at the planet Earth.

Fraser: That is the worst case scenario…

Pamela: Essentially what happened with the small asteroid that blew up over Russia is it came out of the direction of the sun and we just didn’t have early warning and thus a billion rubles worth of broken windows and other damage.

Fraser: I’m getting surprised how big that asteroid was compared to what originally people were saying it was 70 tons and now it’s like 7000 tons. It’s actually a pretty big rock. So now you actually started off in the beginning of the show how this cloud might actually be effecting our view of the universe so can you talk about that a bit more? You’re freaking me out!

Pamela: (Laughs) So it’s probably only a few tens of earth masses worth of material so order 50-100 earth masses at most. That material in some cases is a sphere of basically dust. You have chunks of ice that are colliding with one another that are letting off a fine-grain particle as they crash into one another. If you’ve ever seen the images of geysers coming off of Enceladus there may be material like what you see coming off of the geysers created from the collisions of these objects over the billions of years. We don’t know that for sure. It’s could be that they’re just just nice chunks of ice that because they’re so far apart from one another, collisions are so remarkably rare that it’s a land of no dust… but we don’t know. If there this fine-grained particulate out there, this dust, it could be acting to scatter the blue light that is trying to travel its way into our inner solar system creating this reddening effect on everything we see as we try to look beyond the edges of our solar system.

Fraser: So what impact would that reddening have on our science and our understanding of the universe?

Pamela: It would mean that our understanding of the temperature of everything is just a little bit off. Not a lot but there have been people that have tried to explain some of the cosmic microwave background as perhaps being caused by effects of the Oort cloud. Adding a little bit of clarity or removing a little bit of clarity, people are making guesses and trying to understand what could be possible and we really don’t know. That’s one of the awesome things and horrifying things at the exact same time.

Fraser: For example, specifically, like with the cosmic microwave background radiation. The temperature changes that they are trying to detect are very minute.

Pamela: The nice thing is that this would be a constant effect assuming, and this is another huge assumption, that the Oort cloud has a perfectly smooth distribution. People have taken the time to try and look at that and try and find some sort of a variation that the largest scales could be explained by thickness variations in the Oort cloud.

Fraser: Like when you’re looking through the Hills cloud you’re looking through the plane, if ecliptic through the Oort cloud, maybe you’re going to get a different reading.

Pamela: Right and so these are all things that people are trying to understand. The data that we have so far hasn’t been a in a high enough resolution that we can actually make out any effects to the polarimetry or reddening that could be explained exclusively with the Oort cloud being the cause.

Fraser: We’ve talked about how the Oort cloud is invisible so what would it take to actually get out there and observe objects?

Pamela: A lot of time. It sounds like I’m being sarcastic but we’re talking about .8 light years distance. The best we can really do is wait for object after object to do like Sedna has done and come for a visit and over time build up the orbits of a small catalog of objects that come to us rather than us going to them. That’s the best we can do. More power to folks like Mike Brown who are out there trying to discover the largest objects in the Kuiper belt and the nearest objects of the Oort cloud.

Fraser: I remember, and this is just coming to me now, someone had put together a mission concept to be able to actually get a space craft out in to, at least, the near part of the Oort cloud. It would essentially be a space telescope sent out into the Oort cloud and it would just be observing objects and maybe fly past one if it could find one. It would take, as you said, 100 years to get out to a place where it could some science.

Pamela: Even more problematic than that is, well first of all you have light travel time so the signal time is going to take months to get back to earth if you do get a telescope out there. You’d have to launch a really large telescope though because the Oort cloud will be extraordinarily diffuse This isn’t Han Solo’s asteroid belt. Even our own asteroid belt isn’t Han Solo’s asteroid belt. We’re talking about tens of earth masses scattered over an entire spherical area that is .8 light years across.

Fraser: The kind of civilization that is able to study the Oort cloud is the kind of civilization that could send space craft to other stars.

Pamela: No actually that’s not true because it’s easier to see it from outside our solar system than it is inside. If there is an Oort cloud out there we can detect things like this around other solar systems. Detecting an Oort cloud from outside the system so you can get the distance so everything is compacted down and you are looking through the thickness at the edges. Just like looking at a Nebula, you can’t really see the Nebula if you are inside it. If you want to see the planetary Nebula you fly away. You see this ring where you are looking through the most parts of it. Detecting an Oort cloud you really want to be that other solar system not too far away.

Fraser: So do we see any Oort clouds around other stars?

Pamela: We have seen things that resemble the Oort cloud around other stars so this is where we continue to think that our understanding should be perfectly reasonable. Unfortunately things like nailing down things like exactly what it’s mass is, exactly what is its furthest limit and exactly what its inner limit is and those sorts of details we’re not there yet. In terms of a perfectly rational theory to explain the comets and to explain objects like Sedna, we’re on to something. We’re on to something that’s fairly typical to see within our galaxy.

Fraser: That’s awesome. Well thank you very much Pamela.

Pamela: My pleasure.

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

Transcript: Failed Stars

Astronomy Cast episode 290 for Monday, January 21, 2013 – Failed Stars

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. With me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville.

Hi Pamela, how are you doing?

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

Fraser: Good, did you notice I added that director of CosmoQuest?

Pamela: I did! That’s very exciting.

Fraser: Well we’ve been doing CosmoQuest for so long and we keep forgetting to include it in all the things that we do so for anyone that has never heard of CosmoQuest, what is it?

Pamela: It is an online research facility designed for the public so we work to bring anyone out there who is interested in becoming part of solar system and space exploration an opportunity to engage in the same ways that scientist do. We do science activities, we have weekly seminars and we have a whole range of different ways including forums. We wove in the 1:18… into CosmoQuest. We have a whole variety of ways for you to get involved and I hope you’ll take the time to check it out at www.cosmoquest.org.

Fraser: Yeah you can classify craters on the moon or search for icy objects in the solar system; really our goal is to try and help regular folk combine with scientist to do real science and this is what we’re doing.

Pamela: And we’re succeeding

Fraser: Absolutely, it’s awesome.

Pamela: I have one quick announcement, so sorry. We are in the process of phasing out the Astrogear store because while we love all of you, you don’t buy a lot of things. As we’re working to change out our staff, our wonderful Joe Ray has gone onto wonderful and better things than us and although we’re sad, we’re proud of him. He was the person running our store so we’ll continue to offer our t-shirts in the future but everything else we have is on close-out. If you want to buy things, now is when you should buy things. That’s www.astrogear.com.

Fraser: Alright… buy things… BUUUUUUY THIIIIIINGS. Now can we start the show?

Pamela: Yes, now we can start.

Fraser: If you get enough hydrogen together in one place, gravity pulls it together to the point that the temperature and pressures are enough for fusion to occur. This is a star. But what happens when you don’t have quite enough hydrogen? Then you get a failed star, like a gas giant planet or a brown dwarf. Today we’re going to talk about failed stars. You know failed stars are actually super common, maybe more common than regular stars? There are a lot of them out there.

Pamela: Yeah I don’t think we have enough statistics yet; that’s the crazy thing that we’ve only been finding these things since the 1980’s really and its only been with the 2MASS survey and a few others that we’ve really started to be able to find them in a meaningful way. We’re only finding them by the hundreds but we find red dwarfs by the bazillions basically (laughs).

Fraser: So let’s talk about the process of what it takes to make a star and that will sort of help us understand why things fail.

Pamela: We have entire shows on this, go back and listen to one of the shows on this. In short what happens is you have a giant molecular cloud of gas, dust and all of this material as the cloud gets shocked by something or gravitationally compressed by something. All of this gas begins to collapse and fragment and the individual fragments will begin spinning or sometimes it will split into multiple pieces and this is where binary stars come from. Some of those pieces just aren’t quite big enough to fuse hydrogen and that’s where we end up with failed stars. Where things get messy is where do baby planets come from? In this case you have a fragmenting, spinning chunk of molecular cloud and in its core you end up with a star forming and around that star will be a disk of material. That disk fragments into pieces that are orbiting around the primary star. Now when you have binary stars you end up with two collapsing, spinning bits and the non-disky bit is the star and you can actually end up with disks around both of those fragments that are forming the binary star. This can all get very complicated but the key component here is planets form in a disk of material through an accretion process whereas stars form via the fragmentation of molecular clouds and the collapse of those fragments into things that hopefully burn hydrogen.

Fraser: So really we define that star as that ability that enough mass has come together, enough is going on, that you have that fusion and the star ignites. Our sun, obviously, is one of these stars but they get a lot smaller right?

Pamela: They do

Fraser: So how small can you get when you still have a star? You still get a success ribbon?

Pamela: The cutoff, as near as we can tell, and we haven’t actually found the smallest possible star that you can have yet, but as near as we can tell from theory is between 80 and 85 times the mass of Jupiter. So at a certain point you stop using the sun as your point of comparison and start using Jupiter. Take Jupiter, multiply it by somewhere between 80 and 85 and (6:33) start fusing.

Fraser: If you were going to go the other way and look at, say, the sun, what percentage of the sun would it be… around 10%?

Pamela: So compared to the sun these are tiny objects. These are about 71/2 to 8% of the sun so tiny, tiny, tiny, stars.

Fraser: I always find the process of these red dwarfs really fascinating because they have no radiative zone, it’s all convective zone and the whole things is just churning it’s material and they last a really long time. They can keep the stellar fusion going.

Pamela: This is the red dwarfs that we’re talking about. They’re fully convective so just like with your lava lamp you see the blobs going toward the surface then going all the way back to the bottom. In red dwarfs you have the same process going on where there is nuclear fusion going on in the core, but then the hot material rises up to the surface fully circulating. When a red dwarf finally finishes the hydrogen process it’s pretty much used up everything that can be used up in the star.

Fraser: But it will last, even the small one, will last trillions of years.

Pamela: Yeah, these are the longest lived things in our galaxy.

Fraser: Totally. So that is sort of where we set our limits; anything above 7 1/2% of the sun. There’s really no 100 times the mass of the sun? That’s a big range. Obviously you’re going to end up with clumps of hydrogen coming together at smaller amounts than this 7 ½% of the sun so what do we call these?

Pamela: Those are where you start to get into the brown dwarf stars. These are objects that we define not just how they form but also how they sort of, kind of, but not very successfully for very long do have a fusion process in their core. Brown dwarf stars are objects that are 13 to 80-85 times the mass of Jupiter. At that cutoff they’re able to very briefly burn tritium and deuterium in their cores. These are heavy forms of hydrogen that have extra neutrons in their centers.

Fraser: Where does the extra hydrogen, the heavy forms of hydrogen come from?

Pamela: It’s just one of the components of the universe. If you look around the universe you’re going to find heavy hydrogen.

Fraser: Oh I see, so there is a certain percentage of just a blob hydrogen that’s going to have those elements in them.

Pamela: Yes, just like water. There is heavy water and we can find it in the ocean. It’s just part of the ocean where part of the H2O formed with a deuterium atom and instead of just straight hydrogen.

Fraser: So does this stuff just fall inside the star and clump together, or is it just a percentage of it that’s able to use?

Pamela: It’s just a percentage of it that is easy for it to use. Hydrogen doesn’t burn when it’s missing those extra neutrons nearly as easily as the heavier forms with the extra neutrons in it. Physics in play lets these stars more readily burn and doesn’t allow it to burn hydrogen that is missing these extra neutrons and unfortunately the heavier forms of hydrogen are much more rare.

Fraser: And so because it’s rare, it only a small percentage of the overall object that’s made up from this stuff, how much energy, how much heat, how much can it do?

Pamela: Well at the end of the day it’s only able to burn for only a few hundred million years. You have this fully convective little star that depending on how big it is, in some cases it can actually burn some lithium as well because lithium burns very easily. It’s only for a few hundred million years and once they’re done they’re done.

Fraser: How hot do they get?

Pamela: That’s the awesome thing is that these things are, during their normal observed state in some cases, actually human body temperature on their surface

Fraser: Really?

Pamela: Yeah. We’re looking at stars that, in general, are less than 1000 degrees Kelvin.

Fraser: But way hotter the deeper you go? Jupiter is hotter right?

Pamela: Yeah, totally true but the fact that on their surface they get to be human temperature. Trying to figure out what to do to these has forced us to expand the way we look at stars. We normally have the O’s as the hottest, B, A, F, G. We’re one of those normal G type stars, K, M, red dwarfs and as we start adding new types they had to add an L class which start to have hydride bands and they start to have alkali metal bands and they had to go on to add T class stars. These are stars where we actually start to see carbon monoxide in the atmospheres of the stars. There is a handful of what we call Y type stars and these are stars where we start seeing things like absorption lines from ammonia. This actually made a much more polite and disturbing mnemonic for how we think of all of this

Fraser: Oh Be A Fine Girl Kissed Me

Pamela: Oh be a fine girl kissed me is the normal one that we’re used to but now we’ve added an L a T and a Y so it’s become Oh Be A Fine Girl Kiss Me Later, Thank You.

Fraser: Right so then is there this distinction between these brown dwarfs that are actively consuming and burning these heavier forms of hydrogen and the ones that have run out of fuel. Do astronomers make some kind of distinction between them?

Pamela: No and I honestly don’t know if we’ve observed any that we can specifically say “This one is currently undergoing nuclear reactions.” These are extremely rare objects in our current observational sets. I can’t tell you how rare or not rare they are in the sky but because we’re only starting to observe them we only have so many data points. They burn for such a short period of time that trying to catch one in our few hundred observations as actively burning, I don’t know if statistically we can say we should have done that with certainty yet.

Fraser: Is it one of those situations where it gets to its temperature and then it just takes a really long time to cool down? I know that we talk about stars that turn into white dwarfs then the white dwarfs will eventually turn into black dwarfs but that process is going to take billions and trillions of years for these stars to reach the background temperature of the universe.

Pamela: At the end of the day, these just don’t get that hot. They just don’t get that hot.

Fraser: But they’re still cooling down over long periods of time.

Pamela: They are but it’s not the same way you think of white dwarfs cooling off. With a white dwarf you’re starting out with something that is tens of thousands degrees Kelvin. When they cool off to a few hundred degrees Kelvin and become what we call black dwarfs, that’s a massive change. These guys start out at about a thousand degrees Kelvin and cool off to a few hundred degrees Kelvin so when you’re looking at something like that it’s a very different situation. These are stars that don’t work in the ways that we think of. The smallest of them like Jupiter are supported through normal gas pressure but the largest of them are supported just like white dwarfs through electron degeneracy pressure. Here you have something extremely small and fairly dense but not white dwarf dense. All of them are within 10-15% the same radius. Take Jupiter and add stuff to it and it doesn’t get bigger, it just gets denser. Keep adding stuff and it changes how it supports itself from gas pressure to electron degeneracy pressure. Their temperature doesn’t vary much across the entire range. These things just don’t behave in the way we’re normally used to thinking of stars because they’re not normal stars. They’re this weird transitional object.

Fraser: Okay so I guess the question that I wanted to ask next then was what is the method that astronomers use to find these objects because they aren’t bright and they aren’t shining.

Pamela: Infrared. It’s not just that they’re not bright; it’s that they’re not bright and they’re not really giving off light in useful wavelengths. It’s perfectly possible to detect a very very faint blue object or red object with a normal telescope. Big deal. They’re faint, they’re annoying… we can do it! Now brown dwarfs pose an entirely new challenge because they are so extraordinarily red that the bulk of their light is given off in wavelengths that aren’t readily observed with your normal optical telescope. You have to get above the earth’s atmosphere and you have to start using things like the WISE telescope; that’s one of the instruments that have been used. They are found ground based on digital sky surveys that have done a lot of work to find them. The easiest way to find them is to start looking in the IR. The other problem that you run into in trying to find these suckers is they like to cuddle up next to nice bright stars and so now you have to start doing things like using what are called chronographs which is where you essentially put a disk in front of your stellar disk on the sky, block out its light and look to see if there is anything faint near that bright star. It gets kind of tedious to use a chronograph to look at every bright star in the sky to try and find brown dwarfs that are binary systems. It’s the isolated ones that are easier to find.

Fraser: Right so the point being that if get a situation where the star is in a binary companion with a brighter star, this gives you away to know where to look because they’re so hard to see. I know people are also looking for them in these stellar nurseries right? They’re looking for places where brighter stars are likely to be.

Pamela: Right. We look for them all the places we look for normal stars but they’re annoying to find. We really have to be looking in the IR and in the near IR.

Fraser: Now we’ve got the James Woods space telescope coming out in the next… 5 years? Will that be able to help the search for brown dwarfs?

Pamela: I think that would be a strange use of such a powerful telescope to use it to survey for new brown dwarfs but what it can do and what I expect it will be doing is imaging not just brown dwarfs but also giant Jupiters. We’re now at the point that we are starting to be able to individually look at some extra solar planets; Bitzer has done this in a few cases. They’ve also looked at a few brown dwarfs this way and to individualized meaningful studies of things that are already discovered. It really takes a whole family of different types of telescopes to first survey the sky and catalog what’s there and follow up in detail and understand what those objects are.

Fraser: So it might not be the tool for surveying but it definitely will be the tool for doing full on observations. It’s going to be an enormous telescope. Hubble is like 1.6 meters and this is a 6.5 meter telescope. It’s enormous. That makes sense; it might be a waste of time to be surveying for them. So you actually led into this right? We’ve got this situation where we have these brown dwarfs, the high end of the failed star, but it’s really a spectrum. Wherever you get hydrogen clumping together all the way down to nothing, you’re going to have some situation. Let’s go the other way. As we get smaller and smaller and smaller, less mass, I guess smaller isn’t a good way to put it right because as you said they kind of stay the same size they just get more dense. How does that work on the lower end?

Pamela: On the lower end is where things start to get messy and people start to argue because we can’t, basically, stick a probe inside one of these extra solar planets or brown dwarfs and figure out “Did it ever do any burning?” So what we start doing is start looking if there is lithium in the atmosphere. If there is lithium in the atmosphere it means it didn’t burn lithium so that puts one level of constraint on this system. As we go down people just start arguing. We know that below 10 masses is not a planet. We’re pretty sure that above 13 masses is a failed star; it did have some temporary nuclear burning. In that middle range you have these weird objects snuggled up against stars that we call brown dwarfs but they’re at the 10 Jupiter mass level. It’s thought that there is either some sort of mass loss or something else happened. It’s unclear what to call some of these objects. Are they failed stars, or are they below planets and that’s one where I think a lot of work on the definition still needs to happen and we need better models.

Fraser: Part of it is: “Is it orbiting a star?” But I guess that’s the distinction? “Is it a binary companion or is it a planet going around a star?”

Pamela: If we didn’t watch it form and we don’t see a protoplanetary disk that it’s a part of, we have no way of know if the object we’re looking at formed via an accretion process like a planet or a collapse process like a star.

Fraser: You mentioned earlier on that things like Jupiter, for example, if you add mass to Jupiter or clouded two Jupiters together, you wouldn’t necessarily get a much larger would you?

Pamela: No, you’d get an object the exact same size, more or less, within a few percents. That’s one of the awesome things. It’s one of those cases where the density just keeps going up. The way the pressure and gravity balance, the radius stays very similar as you go from roughly Jupiter sized to one of these 80 Jupiter mass, not-quite-yet-a-star objects.

Fraser: Wow

Pamela: Yeah it’s really awesome, physics just kind of balances out this way.

Fraser: Now if you could look at a brown dwarf what would you see?

Pamela: You’d see a magenta object that has convected cells on the surface. When you look at the sun through a really good hydrogen alpha filter and you magnify it sufficiently you can see these boiling cells on the surface. You actually have convective cells driving brown dwarfs as well. Brown is really a misnomer. Brown isn’t something you get through additive light processes generally. Rather they’re this deep, deep magenta. I hate to say this but they are the color of my hair currently. They’re magenta objects but brown is just easier to say and spell.

Fraser: So they’re sort of a reddish color? They’re on the spectrum of a red dwarf but they are a deeper red? A darker red?

Pamela: Red dwarfs are much more Crayola in color. This is where you start to get that deep maroon color. The MIT “blood on concrete” is the joke they use. That deep maroonish, reddish color.

Fraser: But if you look at Jupiter you see it’s got these bands and storms on its surface and yet when you reach the brown dwarf size you’ve got convective cells blobbing up like a lava lamp. Where does that happen? Or do you go from one to the other?

Pamela: It’s all going to depend. We only have one example of Jupiter so it’s hard to say. What we’re seeing with Jupiter is these different cells where we did an entire episode on the weather of these planets where you end up with different atmospheric levels rotating the planet at different rates. This leads to bands of various colors going at different rates around the planet which causes some to appear to move backwards relative to others and you don’t see the active convection. Now we can’t actually image the detailed surface of a brown dwarf so we’re basing everything we know of what they look like off of models. Based on what we know from models you should end up with convective cells that are visible on the largest of these but at you get to smaller and smaller ones as you start to go from the “later” to the “thank you” part of our mnemonic out to the Y spectrum class stars. Now perhaps you’re going to begin getting that band similar to what we see on Jupiter. Until we have observations I can’t tell you exactly when these transitions take place or exactly when the convective cells begin to get hit by weather patterns in the atmosphere of these failed stars.

Fraser: I know there were some observations of some extra-solar planets where they were able to see that they were tidally locked to their star.

Pamela: Well they don’t see that they are tidally locked.

Fraser: No, they calculate that they were tidally locked and yet the heat was being distributed across the entire planet so there had to be ferocious storms that were transmitting so you would see these bands of these storms as they were swirling around the planet. If you got bigger and bigger eventually that convective process would take over. There is no clear line on where that happens yet, it’s real interesting.

Pamela: This is where we need orbital interferometry. We need the ultra high-resolution imaging capabilities from space where we can be above the atmosphere and hopefully, sometime in our lifetime, the money will be invested to make this possible but until then we have models in our computers and the models are getting better slowly.

Fraser: Now I think there was a great misnomer that flew around the internet a couple years ago and we’ve covered it a couple times in astronomy cast; this idea that the Galileo space craft, the nuclear powered Galileo space craft, if it was crashed into Jupiter that it would ignite and turn into a second star.

Pamela: No… (Laughs)

Fraser: Based on the conversation we’ve just had that that concept was deeply flawed.

Pamela: Deeply, deeply flawed. That’s like saying me squishing a mosquito on my skin will cause me to go thermonuclear. No, it’s not… even if it is a radioactive mosquito that will give me radioactive powers. Yes, Gallo was carrying nuclear fuel on it but that just means that it was giving off a lot of heat as those radio isotopes did their normal half-life thing and decayed and gave off energy and powered emission. It’s not like it was a nuclear bomb nor had that capacity to become one.

Fraser: And even if it was it wouldn’t matter.

Pamela: Right we could blow nuclear bombs up in the atmosphere of Jupiter and it would disrupt the weather patterns for a while but not for that long. We’ve dropped comets… well we haven’t personally…

Fraser: We’ve done that!

Pamela: The solar system has dropped comets in the atmosphere of Jupiter giving off the energy equivalent of nuclear weapons. In the process Jupiter took it on the chin and healed up rather quickly.

Fraser: So the only way that Galileo could do that is if it happened to have 79 times the mass of Jupiter somehow.

Pamela: Yeah and even that is questionable. To guarantee it you need at least 83 times, 84 times.

Fraser: Yeah 84 times the mass of Jupiter packed into that little spacecraft and then it smashes in and boom… it has to be hydrogen too.

Pamela: Maybe if it was that weird red stuff that was theorized in the recent star trek which doesn’t work…

Fraser: Yeah… alright… cool. Awesome, well thank you very much Pamela.

Pamela: Thank you very much.

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

Transcript: Cherenkov Radiation

Astronomy Cast episode 289 for Monday, January 14, 2013 – Cherenkov Radiation

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. With me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville.

Hi Pamela, how are you doing?

Pamela: I’m doing well and I’m love that this is the one and only time I can pronounce something that you mispronounced.

Fraser: Shhhhhhhhhhhhhh! You can do Russian- Sherrainkoff? How do you say it?

Pamela: Cherenkov (chuh-reng-kawf)

Fraser: Cherenkov, see I had wrong

Pamela: (Laughs)

Fraser: In case Preston wants to reuse this: Astronomy Cast episode 289 for Monday, January 14, 2013 – Cheeeerenkov Radiation

Pamela: (Still laughing)

Fraser: Well thank you very much I’m really glad you were able to bring your Russian training…

Pamela: It’s the ONLY time!

Fraser: I know, I know. You learned Russian, all of your training, for this very moment. So we’re going to be at Science Online, by the time you receive this we will have already been to Science Online which was a really cool conference in North Carolina and that’s going to cause a little bit of weirdness. We’re going to try to record some shows live while we’re there, at least hang out from a restaurant or something and do a couple episodes to catch up. Results have been a whole bunch of catch up episodes coming into the feed now; I hope you have been noticing. We apologize for episode 283 we lost the audio.

Pamela: If you want to know how to most effectively destroy a Macintosh with iPhoto streams. I Google plussed to death my computer.

Fraser: So you broadcast its death? Or you Google plussed it to death?

Pamela: No, no I rage posted against the machine.

Fraser: …and it rage quit. Right so we apologize, fortunately we had our backup which was a YouTube video so we were able to extract the audio from there and that’s what you’re hearing. The other thing is I hope you have noticed we have the weekly space hangout coming back into the feed which is fantastic. That’s the show of the weekly hangout of all of the space and astronomy journalists.

Pamela: We really have major kudos for noisy astronomer Nicole Gugliucci for being the force of nature behind hurting the cats to make that happen.

Fraser: That’s what threw me off the rails in the first place and I’m really glad that Nicole has stepped up; it’s fantastic.

Fraser: Sure, our atmosphere protects us from a horrible Universe that’s trying to kill us, but sometimes it prevents us from learning stuff too. Case in point, the atmosphere blocks highly energetic particles from reaching our detectors. But there’s a way astronomers can still detect their influence: Cherenkov radiation; the cascade of radiation that blasts out as a high-energy particles make their way through the atmosphere, like a radioactive rain shower. So Pamela lets go. First: Science. What is Cherenkov radiation?

Pamela: It’s radiation that is generated when a particle passes through a medium at faster than the speed of light in that medium which is a really interesting thing to wrap your head around. As the particle goes through, at faster than the speed of light in that medium, it causes all of the particles around it, depending on what they’re made of, this is specific to dielectric materials to get aligned, then when they collapse back down to their normal state of chaos they give off photons which are organized and you are able to see the distribution of this color of light and detect it. What is really awesome is as you have this particle barreling through some material; it doesn’t have to be just our atmosphere, this could happen with a neutrino passing through special fluids. This is how we detect treatments as well. The shockwave created by its motion through a medium will create a beautiful ring of light and depending on the crispness of the edges of that light, it tells us a lot about what was traveling through the medium.

Fraser: Now I’m going to need you to back up for one second. You said when something moves faster than the speed of light…

Pamela: Through the medium

Fraser: Through the medium… so can you go back. Obviously Einstein would not appreciate something moving faster than the speed of light…

Pamela: In a vacuum

Fraser: In a vacuum, no I understand. So what exactly is going on here? We’ve got this particle moving like a cosmic ray or something right? It’s moving through space in a vacuum, very quickly…

Pamela: Quite happily

Fraser: Quite happily, and it hits the atmosphere and what does it do?

Pamela: It breaks.

Fraser: It can’t go faster than the speed of light.

Pamela: Well that’s the crazy thing. Particles can quite happily go faster than the speed of light through a medium. There’s actually rubidium gas that you can, in a fancy set-up, make light travel at about human walking speed.

Fraser: So you could send a pulse of light, one side through the rubidium, run around to the other side and catch it on the other side before it makes it out?

Pamela: It’s hard to catch light but yes. Because the propagation speed of the phase of the wavelength through the medium is so slow in some cases I could actually, if I wanted to be in the rubidium gas, I could walk faster than the particle of light through the gas. That’s cool. Now in everyday reality, light traveling in our atmosphere travels slower than it does when it passes through a vacuum and in fact a particle traveling at relativistic speeds or even at the speed of light, in the case of gamma rays through a vacuum; when it starts passing through our atmosphere it starts undergoing breaking processes. These are energetic particles, these are charged particles and that charge influences the area around them. Moving charged particles generate electric and magnetic field effects and there are a bunch of different types of materials. We normally talk about conductors. The wires in the wall conduct electricity, they conduct telephone signals, they conduct a lot of different things. Then we talk about insulators. The wood of my desk is not going to allow a random sparking “something” to electrocute me. The plastic coating over the wires is going to protect you from being electrocuted. In between the conductors and the insulators is what’s called dielectric material. This is material that doesn’t so much transmit the electricity but unlike an insulator which just doesn’t care about the electromagnetic fields, a dielectric material is actually going to have all of its little charges happily flipped to coordinate; they are going to polarize. This is how they respond to the charge. It’s a higher energy state to have all of the particles flipped and line up. Normally they are nice and chaotic and everything balances out to neutral. When you have this high speed charged particle moving through, it causes all of the stuff and dielectric material to line up. That happens even when it’s going slow but what’s awesome is, when it’s going really fast the reemission of the energy of the lining up of all of the particles in the dielectric is coordinated and you get this Cherenkov radiation.

Fraser: Got it. Ok. So then what kind of events, what kind of particles stuff, is going to be causing this radiation?

Pamela: There are various different types of places that we observe this. With air detectors, detectors out in the open often in big observatories and tops of mountains, you are looking for the cascades of light created by cosmic rays entering our atmosphere, gamma rays entering our atmosphere interacting with the atmosphere. In underwater situations you are looking for neutrinos, you’re looking for (??? 9:36)

Fraser: We did a whole show on cosmic rays and neutrinos. The difference between a gamma ray and a cosmic thing sound like the same thing but they’re different right?

Pamela: So a gamma ray is just a photon, a very energetic photon, a very, very… we don’t have a word for higher energy light than this so gamma rays are just particles of light that are extraordinarily high energy. Cosmic rays can actually be particles so this isn’t a photon. This is something that has mass and it’s traveling at relativistic speeds so it’s not actually going at the speed of light but it’s going fast. They’re often generated in things like super nova explosions or high energy jets in a variety of different things like jets coming off of AGN, active galactic nuclei. When these high energy charged particles hit our atmosphere they start breaking but they also, while they are moving so fast, cause this coordinated emission of radiation that we detect as Cherenkov radiation.

Fraser: I think the big key here is that they are the most energetic events that we see in the universe. It’s the same thing with x-rays, with gamma rays, and with cosmic rays. By every measurement you are at eleven with them.

Pamela: (Laughs) Yes

Fraser: Normally if we didn’t have our atmosphere these events would be killing us with radiation… so thanks atmosphere. We need spacecrafts to view them.

Pamela: Right, and even with spacecrafts we can’t detect the Cherenkov radiation that comes from things like neutrinos passing through the various heavy water detectors we have on the surface of the planet. Cherenkov radiation is one of those amazing things that can be used both in astrophysics, in particle physics and in a variety of other subjects that are beyond what we can talk about in just these 30 minutes. Just focusing on those two different applications: Cherenkov radiation is how the Super Kamiokande reactor in Japan is able to detect neutrinos from our sun and neutrinos being emitted in a variety of nuclear reactors. What’s really actually kind of awesome, to me at least, it can differentiate between the different types of neutrinos based on how crisp the doughnuts of emitted light are as these neutrinos create the Cherenkov radiation with a neutron neutrino it creates this beautiful crisp doughnut of light that can get detected, whereas an electron neutrino because it creates multiple propagating cones where it triggers things that trigger things that trigger things that creates fuzzy doughnuts of light. Just looking at the type of radiation that’s created starts to tell us a story of what created it. This isn’t just a way to detect high energy stuff, it’s a way to detect and differentiate between different types of high energy stuff.

Fraser: So then there are a few Cherenkov radiation detector facilities set up around the world right? There’s the Pierre Auger…

Pamela: There’s the Pierre Auger observatory but that’s only one of many different types. It’s actually a really weird hybrid facility. It’s located down in the Andes Mountains and they use a variety of different detectors that look for fluorescent materials that are specifically detecting neurons. They’re trying to figure out how they can detect this in radio waves. It’s a kind of neat R&D facility that’s looking for a variety of different types of events. More classically people have used what are called air Cherenkov detectors. Whipple telescope was one of these and it’s one of the neatest looking telescopes. It’s this outdoor, fully-exposed facility that has a million, not literally a million, but a bunch of little tiny mirrors that are all mostly lined up with one another. What’s awesome about trying to detect this is you don’t need to have a perfect surface; you’re just trying to detect the full blob of light propagating through our atmosphere so you don’t need to focus it or anything. They have these big outdoor light collecting surfaces made of multiple mirrors that focus the light up to detectors that look at the distribution of wave lengths of light. By looking at all of the different colors that are given detected and all of the different timings of the detection and how the mirror is getting hit they’re able to figure out where in the sky this new cascade is coming from and tell various characteristics about it. You can see the cascades that are caused by gamma ray bursts and the cascades that are related to various other events. It’s kind of neat that there is a future for the badly focused telescope and it’s called detecting high energy particles.

Fraser: So you’ve got all of these different detectors set up across the landscape and as you mentioned you’ve got these cones of radiation coming down and these detectors are then letting them backtrack where the event came from right?

Pamela: Exactly. One of the frustrations with a lot of these detectors is you have this event that takes place at high, high up in the atmosphere that causes secondary particles to get generated that cause a Cherenkov light degenerated by all of these different cascading particles so you end up with a lot of these little different cones we use in air detectors. All of these cones from all of these different reactions end up creating this vast… it’s often referred to as a pool of light in the atmosphere that then only part of this pool is getting captured by the air Cherenkov detector like Whipple. It’s a much less precise science when you compare it to, say, the vast array of photomultiplier tubes are used to very precisely look at the doughnuts of light coming out of a single particle reaction within one of the Super Kamiokande tanks. When you’re looking at atmospheric things it’s just a mess but it’s a mess we can turn into science. Then when we were looking at single particles in the swimming pool detectors, essentually, we have these beautiful precise reactions of particles that in some cases have traveled all the way up through the earth. It’s neat to combine all of these different thing to try to learn about… it’s the same process in every case it’s just the same process getting triggered in a variety of different ways.

Fraser: We mentioned the Whipple observatory and how it’s sitting out on the landscape and there are all of these detectors. What do these water tank detectors look like?

Pamela: Basically, take an old mine underground, create a large spherical pool within it, line the walls of the sphere with photomultiplier tubes, fill the whole thing up, close the hatch and hope you never have to go back inside because if you do, something broke. They’re basically giant tanks underground waiting quietly for something to interact inside of them.

Fraser: We did a whole show on neutrinos again and talked a bit more about those tanks, but you’ve got this same situation where you’ve got a neutrino passing through this medium, this water, and you’re hoping that it’s going to interact?

Pamela: It’s again that Cherenkov radiation that we’re looking for. We have so many of these detectors scattered all over the planet. We have the ice cube neutrino observatory down in Antarctica, there’s super Kamiokande in Japan, and then we have the air observatories also scattered about the planet. One of the frustrating things, at a certain level, is with some of these things you’re detecting events where the particles traveled all the way through the planet so you can actually see the various detectors scattered through the world lighting up as these events take place. You can use the speed of light and the variation in time between when the different detectors light up to pin point, vaguely, where in the sky the event came from.

Fraser: I love the fact that you can put your detector on the other side of the earth where the event happened and still detect it and still see the particles making their way through the earth and catch them in your…

Pamela: Neutrinos are annoying that way

Fraser: Right, but you could have a planet Earth a light year across and still detect particles because they’ll go through a light years worth of lead.

Pamela: Neutrinos just don’t like the electromagnetic force. They don’t interact very strongly with anything.

Fraser: So our friend Nicole the noisy astronomer always says that she likes radio astronomy because you can go out and observe in the day and in bad weather, it doesn’t really matter. I think neutrino observers have it taken to the next level.

Pamela: But they’ve had a whole new level of frustration.

Fraser: I want to talk about the big sighs. What are some of the big questions that astronomers have been working on? I think one is just this concept of cosmic rays and what is causing them.

Pamela: Well cosmic rays is one of the issues. We know from taking digital images that there are these random bright explosions in our images where five or six or more pixels will get completely saturated as a cosmic ray hits the detector and overloads those pixels on the detector. We know over time that detectors in space gradually get burnt out by getting hit over and over again with these highly energetic particles. Trying to understand where these suckers are coming from has been a challenge that looking at this allowed us to take on. Looking at this has allowed us to pin point these high energy places in our universe that are accelerating particles generally using magnetic fields. That starts to tell us: Let’s just accelerate more things with magnetic fields. That starts to lead us to concepts like ion drives. Not entirely appropriate but one reasonable analogy to look at is an ion drive is just generating cosmic rays flying out its rear end. The cosmic rays fly in one direction and the spacecraft accelerates in the other.

Fraser: In the case of the cosmic rays that are hitting the atmosphere or these detectors, you’re looking at something that has amounts of energy that baffle the imagination, I mean, there are giga-electron volts.

Pamela: Yeah, nothing like a helium atom that has had its electrons stripped away hitting with enough energy to cause vast arrays of atmosphere to cascade with light and its cool.

Fraser: The challenge is, as you said, these things are hitting the CCD’s, they’re going through the back side of the camera and smashing into the CCD’s so it’ really hard to get a fix on where they’re coming from.

Pamela: Yeah, and not all cosmic rays come from space just to be clear. One of the problems I ran into in graduate school observing at McDonald observatory was the 30 inch telescope I was using, it’s dome was kind of cut into the side of the mountain and we had a radiation from granite issue going on so there was a high energy background of cosmic rays being generated by radioactive decay processes right there under foot. Cosmic rays from space, cosmic rays from ground it’s not the same energy and it’s not the same origin, clearly. Equally annoying on the detector and you really need to have, if everything’s getting saturated, you have to keep building more and more sensitive to higher energy detectors to start differentiating all these things that my little optical detector was getting blown out by.

Fraser: I really think that this is one of the great advances with the Cherenkov detector rays is that you finally can get a fix on these things. We don’t want to ruin the story here, you should definitely go back and listen to our cosmic ray episode, but what turned out to be generating these particles is really neat.

Pamela: Right, so there are things like high energy magnetic fields with active galactic nuclei so you have a black hole busily consuming material and as it’s busily consuming material you end up with the discs spiraling around it because conservation of the angular momentum prevents things from falling straight into a black hole except under very specific special alignments that don’t generally happen in reality. This disc is spitting non-neutral material, generates a very powerful magnetic field and that magnetic field can basically act like an ion drive and fling particles at high velocities. We see these also coming from the discs around different stellar events: white dwarfs, stellar mass black holes, neutron stars. They can all have varying degrees, these different types of jets. We also see this coming out of supernovae from hyper novae and from gamma ray bursts. Our high energy universe that our previous generation of astronomers never would have imagined.

Fraser: We always note how if you ever watch Cosmos, in the first couple of episodes Carl Sagan mentions that we have these quasars but we don’t really know what they are. He offers a few suggestions but now we know it is black holes with millions of times the mass of our sun with these incredible warped up accretion disks around them with these huge magnetic fields and that’s what capable of firing out these particles at such high energy levels.

Pamela: This is very new knowledge. As recently as when I began graduate school, faculty were still drawing small monsters squatting in the centers of galaxies as the cause of AGN’s and it was only towards the end of when I was in graduate school, the beginning of this century, the beginning of the 2000’s, that we have finally nailed down, “Yes there are black holes in the center of galaxies.”

Fraser: I really love this idea of being able to use: you can’t look at the phenomenon directly but you can look at it by some other effect like a reflection or an echo. It tells you as much as you need to know, or you can know about the original event. I think this is a fantastic example of how scientists get super clever about “We gotta figure this out, we can’t look at it directly but maybe there is something else we can see”.

Pamela: Unlike gamma ray telescopes in orbit or x-ray telescopes in orbit, using Cherenkov radiation we start to get additional information because there is this cascade of particles that is getting created and there is this cascade of radiation that’s getting created. In some detectors, specifically the ones used for particle physics we’re able to start getting at both the mass and the energy of what’s creating this Cherenkov radiation. Its starts get to us actual information about the particles involved as well as the direction, the source and the light involved.

Fraser: Well thank you very much Pamela that was fantastic. We’ll see you in a couple of days.

Pamela: Ok we’ll see you in a couple of days.

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

Show Notes

• Sponsor: 8th Light
• Cosmoquest
• Mercury Mappers
• Astronomy Cast on iTunes
• Phases of Matter – NASA
• What is Plasma? — PhysLink
• Bose Einstein Condensate – NIST
• Unusual Properties of Water Molecules — Dummies.com
• Video of matter changing states — HowStuffWorks
• Electron degenerate gas
• String Theory Helps to Explain Quantum Phases of Matter — Scientific American

Transcript: Phases of Matter

Fraser: Astronomy Cast episode 288 for January 27^th, 2013, Phases of Matter. Welcome to Astronomy Cast our weekly fact based journey through the cosmos. We hope you understand not only what we know, but how we know what we know. My name is Fraser Cane, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay a professor at Southern Illinois University Edwardsville. Hey Pamela how are you doing?

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

Fraser: Doing great. I know you’re very cold…

Pamela: I am.

Fraser: …so hopefully during the show you don’t slip into some kind of hypodermic state and pass out in the middle of it. Now have you got any interesting things going on in Cosmo Quest that you might want to mention?

Pamela: We are beta testing mercury mappers, we are going live with a whole series of cool hang-outs that are related to Astronomy Cast and I think pretty much all of us, and this includes you, are going to be at science Io this year so be sure to come by, say hi, and we might even have shwag in our pocket to hand to you.

Fraser: I’m going to be doing a talk on the virtual star parties at Science Io for 15 minutes and I’m going to try and get some astronomy happening live while we’re doing it. Should be great. Now one quick thing, if you’re listening to the show and you really love it, if you could go to iTunes and write a review for us that would be super fantastic. The more reviews will help pop us up to the top of the rankings and the listings. Then when people are looking for a show to listen to, they will see ours and give it a shot and that really helps us out. So if have a few seconds and you have never reviewed Astronomy Cast that would help us a TON. That’s over on iTunes so just look for Astronomy Cast on iTunes and there is a way to review. If you’re not a member if iTunes, you don’t like Apple, don’t worry about it, we’re not going to hold your feet to the fire.

Fraser: So as we learn early on with water, matter can be in distinct phases: solid, liquid, gas, and plasma. It all depends on temperature and pressure. Why do different materials require different temperatures and what is actually happening to the atoms themselves when as the material switches fazes. I think I can remember chemistry class, physics class back in high school when we would delve into the phases of matter. The teacher said “…and then there is plasma” I remember solid, liquid, and gas but plasma? Can we kinda take it back then and talk about early scientist beginning to delve into the phases of matter.

Pamela: Well I think it’s one of those things that is pretty much as far back as people were willing to conduct science we have had a basic idea of elemental forces, elementals in general, earth, fire, water, and air. Part of trying to break down this universe we live in is trying to understand how things transition between solid, liquid and gas. The only things we had a firm understanding of for a long time were things like metals, which you have to make fairly liquid to make all the cool things you need to wage war like swords. And clearly things like water where you went from ice, to drinkable, to steam, but trying to understand this there is this basic motion that: Heat something up, make fire, fire changes the state and then when things cool off the state changes in the other direction.

Fraser: I guess they knew pretty early on that water in the solid form and water in the liquid form and water in the gas form were all the same thing, that they were all water. They got pretty comfortable with that idea that you could move these elements back and forth. They did have some pretty goofy ideas about the different elements: earth, air, fire, water, alchemical. How did all that play into it?

Pamela: In general in trying to figure out the basics really took until we started getting to the modern scientific revelation; up until we started realizing that atoms exist. It was hard to comprehend what gas is when we couldn’t separate out the different constituencies of the gas. The phases of matter, well the big picture idea: solid, liquid, gas, is an old concept. The scientific idea of it is only a few hundred years old.

Fraser: Ok, so, what is actually going on here. We’ve got our water, it’s turning into gas or its turning into ice, or plasma, what’s actually going on?

Pamela: (Laughs) So what we’re doing is we’re changing how that actually atoms or molecules of a different compound are connected to one another. When you are dealing with a gas the atoms are completely not connected to one another so they are flying free and they’re going on collisions where they bounce off of one another. They have no bonds keeping them as part of a whole. When you start to deal with liquids you’ve cooled things down enough so that their velocities, when they come together, they kind of stick and then it’s as if you have multiples together and these two might go to become connected and these two become connected so you have more like a square dance of atoms and molecules where they slowly change off how they’re generally ionically bound to one another. As you cool things down even further then you start to build solid bonds where these two, and these two, and these two and all of the different combinations lock together in various ways. Depending exactly on the atomic structure, what you’re dealing with, in some cases, you can get beautiful crystal formations, in other cases you just end up with a haphazard way of mixing the different atoms and molecules into a solid. So these are the three basic phases of matter but then you can end up with some specialties so as you transform into a plasma, plasma is still a special form of gas. In the case of plasma, the electrons are excited and as they bounce between different energy levels and they actually leave their host atoms and molecules they give off light. When you’re looking at a fluorescent light bulb, that’s a plasma. When you are looking at a star, that’s a plasma too. When you go the other direction to Bose-Einstein condensate, which is where you cool special types of gas down to a millionth of a degree or so, at that point they take on very special atomic properties again and in this case you end up with a really funky clump of material where all of the atoms achieve the lowest energy states they can while not having overlapping energy states.

Fraser: So is the Bose-Einstein condensate a special form of matter? Does it work as one of the phases of matter?

Pamela: It’s depending on who you talk to. They’re either going to call it a special state of matter or a special phase of matter. It’s definitely not a solid. This is something where they typically make Bose-Einstein condensates out of rubidium atoms and when they super cool these Rubidium atoms they end up clumping up into a very strangely moving blob. It’s this weird “other” and it’s not determined by the bonding like you do between solid, liquid, and gas. Rather it’s defined by the energy levels of the specific atoms and how they all strive to get to the lowest possible energy level that they can.

Fraser: I think it’s absolutely fascinating how they do this. Don’t they shoot a laser at the Rubidium atoms to extract energy from them until they move into this stage?

Pamela: It’s a two step process to create a Bose-Einstein condensate. First step is you have a set of magnetically bound together rubidium atoms but they are all moving in a swarm. That movement has its own energy so as long as those suckers are moving you can’t achieve a millionth of a degree. So they tune lasers to slowly but surely confine the velocities of these atoms to a smaller and smaller and smaller velocity and they actually have to do things like take into account what is the specific doplar shifted energy level of the electrons inside of the rubidium. Because they have color matched the color of the laser to the color of the transition of the electrons in the rubidium, at a specific, the rubidium is moving velocity. They are able to change the velocity much in the same way you would imagine someone is roller skating towards you and you throw a basketball at them and when they catch the basketball is slows down their velocity. It’s kind of a crazy process but it works. As they slowly tune the color of the laser, they’re able to get the rubidium atoms moving at lower and lower velocities. That’s step one. Step two they actually use evaporative cooling, so just like you cool off by evaporating water off of your surface; sweating is a more normal way of saying that, they are able to cool down the Rubidium by stripping away the faster moving rubidium off of the surface.

Fraser: Now does anything change with the property of the matter apart from the way the molecules are bouncing around; whether they are locked like soldiers in the Bose-Einstein condensate, or if they are in a solid or a liquid or a gas. Does anything change about the matter’s nature?

Pamela: Well the first thing that was noticed when they were creating the first Bose Einstein Condensates, almost; they didn’t quite get it cold enough, but when they were first trying to create Bose-Einstein condensates out of helium 4, they noticed it created what is called a super fluid. This is a fluid that experiences no frictional forces as it flows and so this weird, absolute lack of friction, is one of the cooler properties as you approach getting to a Bose-Einstein condensate. Then you also end up with basically everything, when you look at the distribution of it, it will spread itself out in funky ways, you’ll end up with material trying to climb the sides of containers. It just behaves in odd ways. One of the problems that we have is that it takes a whole lot of effort and energy to create one of these Bose-Einstein condensates. That sounds kind of strange that it takes a ton of energy to cool it off so it has no energy but that’s the reality of what we’re doing. We can only create basically a miniscule amounts of this so we don’t fully understand all the properties yet because we’re just not creating it in large amounts yet.

Fraser: As you move from, say from solid to liquid or liquid to gas or even gas to plasma does the matter itself take on different properties chemically or is it just the same stuff but a different phase?

Pamela: (Laughs) Well the atoms are certainly staying the same but what’s changing is the kinematic motions and the kinematic motions of a certain degree decide how well atoms are or are not bond to one another. Depending on the situation when you have a solid, you have all of these atoms that are very close to one another, and in some cases, are what is called ionically bound to one another. Ionic bonds are when two atoms are sharing electrons back and forth but it’s not that hardcore bond that you get from things like H2O which is a covalent bond. If you have atoms that, when you put them together their electrons essentially complete one complete shell of electrons. It’s like two puzzle pieces where one has the sticky-outty bits that matches the other one’s inny bits. Atoms do that as well and it’s through those types of ionic sharing electron bonds that you’re able to get metallic solid for instance.

Fraser: Now is that one of those one of those situations like with water. I know with water when it freezes is actually becomes less dense right? and floats on top of the water?

Pamela: Water is a bizarre substance. It’s one of the very few things that does become less dense as it becomes a solid. What’s happening here is a liquid, as atoms flow past one another, very temporarily, sharing one another’s electrons but in a very loose way where the kinetic energies that are causing the molecules to flow, those kinetic energies are greater than the binding energies that are trying to hold the atoms together. As they cool, as the motion slows down, the atoms form crystalline structures and it’s the nature of the crystalline structure that causes the atoms to get pushed apart into very specific configurations that cause the solid to end up having a much lower density than liquid does.

Fraser: Now obviously we’ve all experienced this. You leave an ice cube out on your table and it’s going to melt. This is a phase change. What is going on with these phase changes? What needs to be there for you to be able to get these changes?

Pamela: Well in order to go from one phase to another you have to add energy to the system that gets the atoms moving, gets the molecules moving, depending on what it is. When you take, for instance, lead. Say you have lead… I hope it’s not a food implement, lead is poisonious. Lets go with iron. Iron won’t kill you as readily. Lets say you have a nice iron old fashioned dagger of some sort. I don’t know why but you do. It’s a nice friendly solid.

Frasier: Dagger? Really? …anyway I won’t question your analogies, please continue

Pamela: (Laughs) So if you take something that will release energy when burned like wood, it releases that energy in the form, quite often, of infrared and other forms of light. So you stick the dagger on top of the fire and it’s probably more than just wood, and as the temperature increases, as more and more radiation, radiated light, is concentrated on that dagger the atoms will start trying to move, trying to move, trying to move, and eventually the heat energy that has been injected into those vibrating atoms are going to exceed the binding energies and it’s going to begin to melt. Now eventually were you to use something a whole lot hotter than wood; a whole lot more releasing of energy, you could actually convert that into a gas in which case you are completely breaking down all the abilities of the atoms to bond onto one another and their kinetic energy is so great they simply bounce off one another when they come near instead of bonding to one another.

Fraser: And if you go the other way? Right? If you’re extracting energy from the system, heat from the system?

Pamela: Well extracting energy is a difficult process involving laser beams.

Fraser: …well if things are cooling down?

Pamela: If something is able to radiate its heat off into the surrounding using its own infrared radiation. So you take your red hot dagger and you set it aside and that red hot is IR radiation and optical radiation escaping. As it cools down it’s losing energy to its environment so losing energy to the molecules with gas around it, losing energy in all sorts of ways thermal transferred to the surface beneath it and as it cools down the kinetic energy of the molecules are slowing down and eventually have all of the atoms pretty much locked together into this solid form.

Fraser: Now you can get situations where matter can jump forms right? You can get things that can go from solid exactly to gas like frozen carbon dioxide.

Pamela: It’s sublimate, yes. There is (SOMETHING) called phase diagrams and at different points there is, for instance, a triple point of water where at just the right temperature, pressure, density combination you can have water going from solid to liquid to gas with just the slightest changes and so this is that magic triple point where water can exist in all three phases depending on which direction you approach it from. Depending on the density pressure you get lots of different things that can go from this solid to gas phase. On the moon you can have water-ice that can sublimate into water-gas. On the surface of Mars you can have carbon dioxide or water and both will go straight from liquid to gas and this is simply a matter of, at these pressures, there is nothing holding the atoms together so as they go from being bound together in a solid they simply bypass that stage where they are slightly bound together as a liquid and goes straight into a gaseous form.

Fraser: And so pressure is kind of the magic ingredient with this. I know when you buy a hiking stove and you go up to a high altitude and boil water it takes you less time?

Pamela: A lot longer.

Fraser: It takes you longer, that’s right, since the pressure is lower

Pamela: Right

Fraser: So you can have situations as well where you have conditions of very high pressure that change everything as well. You can think about passing down through Jupiter where they have tons of different types of water-ice.

Pamela: Well what’s interesting is you can actually boil things simply by changing the pressure under which it is. So you can end up boiling water by lowering the pressure that it’s under. You can turn nitrogen into a gas, and nitrogen into liquid just by changing the pressure that it’s under. When you’re trying to figure out what phase of matter you’re looking at, you have to consider the pressure, the density of the atoms, the temperature and it’s from all three of these things that we are able to figure out what phase we should mathematically have at the end of the day.

Fraser: So what are some extreme environments that we can find unusual situations. You’ve mentioned one already which is that if you have ice on the moon it going to be sublimating straight from ice into gas. Another is in Jupiter you can encounter different kinds of ice which are produced at different pressures right?

Pamela: There to be specific you’re dealing with different types of gaseous ice and while water does have different crystalline structures depending on how quickly or how slowly you cool it down, I think the best way to consider this is look at Titan. It’s a methane environment that’s very similar to earth. Here on Earth our environment allows water to be liquid, solid or gas depending on very minor differences in your kitchen. If you go to Titan you have the exact same boundary conditions for methane. You have methane rain coming from the sky, methane ice on the surface, methane gas in the atmosphere and so I’ve dealt with thinking about this for so long that it’s not weird or extreme, it’s just the way Titan is.

Fraser: It’s plenty weird just so you know.

Pamela: (Laughs) I think the most interesting application of this, in some regards, is if you very, very slowly cooled down water-ice you can end up with perfectly clear ice that looks more like glass than your normal “has all types of white flaws in it” ice cube. One interesting application of this is if you make a perfectly spherical ice cube, it will melt slower and you can use it in whiskey to have whiskey that is at the correct temperature and isn’t too watered down. It’s always good to know how to use chemistry to make the perfect glass of whiskey.

Fraser: (Laughs) Right of course. I’ll use that in scotch. What about really extreme places like say the surface of neutron stars and inside white dwarves and things like that? Is it still just solid or have you reached some other phase of matter? We call it degenerate matter right?

Pamela: Electron degenerate gas and this is again one of those things where it’s hard to think of it as another phase of matter but it’s definitely a different  behavior at the atomic level. This doesn’t have as much to do with the kinetic properties of matter the way solid, liquid, gas, has to do with the kinetic properties but rather this has to do with how the electrons and the Pauli-exclusion principle come into play. With Bose-Einstein condensates you have to worry about what are the energy levels of the atoms. The atoms each actually only have specific allowed energies but with the electron degenerate gas and white dwarf what you’re worrying about is, what are the energy levels of all of the electrons because the atoms are so tightly packed together that the electrons basically form a crystalline structure where they are trying to avoid having two atoms with the exact same, spin up, spin down characteristics and the same energy level; Pauli-exclusion principle will not allow that. You end up with the latest work of electrons that the atomic nuclei are suspended within.

Fraser: So it’s still a phase of matter then? It’s a gas?

Pamela: It’s a crystal. So it’s a solid. Electron degenerate stars are for the most part solids and we think that there carbon atoms form diamonds actually but it’s the electrons that have this quantum mechanical defined nature that says “the electrons can only get this close and no closer” and so thinking of the different phases of matter isn’t entirely how a chemist would want you to think of it I don’t think. It is a different behavior of the atom at a quantum level.

Fraser: So the last thing that I would like to talk about is plaaaasma. The sun is, what is it, a miasma of incandescent plasma? No? It’s a “They Might be Giants” song?

Pamela: Yeah

Fraser: What’s going on here. How do you turn a gas into a plasma and what is the nature of plasma?

Pamela: So, plasma is a special type of gas. If you’re trying to do the mathmatics of how do the atoms move, how do they collide off of one another, that’s still all related to standard gas laws. What makes a plasma different are the electrons inside a plasma are excited to higher levels and excited things, excited electrons, don’t stay excited permanently and as they cascade back down to the lower energy levels they give off light. Day to day the gas around us is not emitting light. This is good because if the air in this room were emitting light I couldn’t see my screen in front of me so plasmas tend to be okay at a certain level because they are so busy giving off light that light can get through them. This light that is bouncing around inside the plasma actually helps feed the system because a photon emitted in the transition of one atom can go out, hit another atom, cause it to get excited, and you end up with this feeding system but due to the random nature of the directions that the light is coming off, you do end up with light eventually being emitted. Lasers are actually a special case of this where you end up with coherent stimulated emission. We’ve done an entire show on this that you can go back to listen to. With the plasma you simply have over excited electrons that are getting excited through the various collisions and through energy being driven into this system in your fluorescent bulb, it’s the electricity from the wall. In the sun it’s the nuclear reactions going on in the center. Whatever the source of energy that is exciting all of the atoms, their electons are the ones that are expressing that excitement by getting excited and then collapsing and giving out light in the process of the collapse.

Fraser: But you get some interesting properties with plasma. One, it glows with the neon sign, which is nice that it’s not filling the air, but also, we get situations where plasma coming from the sun interacts with the earths magnetic field, and

Pamela: They’re charged particles at that stage

Fraser: Yeah, yeah, and now you have this situation where you can move it around with a magnet.

Pamela: I think moving it around with a magnet is a very strange way to think of it because now I have this idea that “yes you can move a magnet around on various types of plasma and actually see the things moving” but magnetic fields is actually what that magnet is creating. Moving charged particles generate a magnetic field and magnetic fields move charged particles. It’s this neat dynamic interplay. Plasma when it’s in motion generates magnetic fields and standing magnetic fields can move the plasma and that’s just kind of cool.

Fraser: That is really cool.  So do you think there will be any more phases of matter every discovered or has it sort of been fully explained?

Pamela: I think in terms of the kinetic states of energy I think we’re good. In terms of weird quantum mechanical states, we still don’t know what the heck to make of the inside of a black hole. I think just like Bose-Einstein condensates are weird quantum mechanically defined structures just like electron degenerate gasses are weird, quantum mechanic defined way of mass being. I think inside of black holes we have yet to figure out what the heck that is and there’s the potential to either be raw bits, particle physics at play, or maybe even some new structure we can’t even imagine.

Fraser: Let’s just assume its another form of matter which can’t….

Pamela: Yeah, yeah I don’t do that (Laughs)

Fraser: Okay, well thank you very much Pamela that was great.

Pamela: My pleasure

Show Notes

• End of the World…Not!  Cruise
• Sponsor: 8th Light
• E=mc2 Explained by several scientists – NOVA
• Asteroid impact calculator — Imperial College London
• The Manhattan Project
• Energy-Matter Conversion — NASA
• What are anti-particles? – Of Particular Significance

Transcript: E=MC^2

Fraser: Astronomy cast episode 287 for Monday, December 31^st, 2012, E=MC^2

Fraser: Welcome to Astronomy Cast our weekly fact based journey through the cosmos. We hope you understand not only what we know, but how we know what we know. My name is Fraser Cane, I’m the publisher of Universe Today, and with me is Dr. Pamela Gay a professor at Southern Illinois University Edwardsville. Hey Pamela how are you doing?

Pamela: I’m doing well how are you doing Fraser?

Fraser: Good, and we’re back from our awesome cruise in the Caribbean with 90 of our astronomy cast friends… and that was super fun.

Pamela: Yes, and we are going to be repeating this. Look for news aboutHawaiiin January 2014. I’m working on putting together a website on that. All the photos from this year will go up and information for next year will follow.

Fraser: Yeah, it was a really wonderful experience. Big thanks to the folks who did the end of the world cruise for inviting us onboard and letting us participate, we had a great time. Both with being able to see the ruins and do the excursions, but also, just to be able to spend time with the astronomy cast fans. It was great. You put together a really busy schedule where we were recording shows almost every night or doing events, meet and greet party, doing shows, stargazing every night out on the back of boat, we did lunches and dinners with the fans. We had the chance to hang out with almost everybody that came and so it was great to get to know everybody and of course to hang out with you, and the families got together. It was really a fantastic time and I can’t wait to do it again.

Pamela: I have to send out props to Victoria, Eric and Phoenix for all the help the day we went to Copa because you abandoned us and they helped us bring up the front.

Fraser: (Laughs) Yeah, yeah. Abandoned you… I didn’t want to send my children in to that nightmare gale force storm. But anyway,

Pamela: You made the right choice. We had the ferry ride of evil that you can read about in the future in my blog.

Fraser: Yeah we got some great pictures and so like you said it was a great chance to experiment and it was great to hang out with everybody but the downside was it wasn’t the best platform for doing astronomy related stuff because the boat moves at night and then it stops during the day. You’re carrying around horrible light pollution. The boat is moving so you can’t set up telescopes. So it wasn’t a great place for the kind science that we want to do so that’s why we’re going to look for a place that’s on land that’s near a nice observatory and we’ll figure that out. More news coming, just wanted to give everyone a wrap up, it was a fantastic time. Cool, Lets get rolling then.

Fraser: So, its mind bending to think about think about this but the light in your house and the house itself are really the same thing. Matter and energy are interchangeable. This was the amazing revelation made by Albert Einstein with his famous formula E= MC ^2. This is the process that the sun uses to turn hydrogen into radiation through fusion, and the terrible danger from nuclear weapons. So I think I can remember that being when I finally wrapped my head around this, and we did it in physics class in grade 11? Grade 10?, When we were given that formula and now we understood what that formula was about and we had to calculate, here’s your energy, how much mass, how much energy can you release, that they’re interchangeable. That was for me, it really felt like I looked at the whole world in a different way, because you’re so used to these things being two different things and now they’re not. So first let’s talk about this equation. What is it saying? What is it talking about?

Pamela: Well at the most fundamental level it’s saying that if you take something, it has a certain amount of material that makes it up and that material can get transformed into energy. But the thing as a whole has a sum of energy and mass that is a constant so you have the energy of a constant that is tied up in its rest mass and it’s kinetic motion and then you have the fact that if its moving, its matter amount doesn’t change. Its matter is dictated by how many electrons how and many protons does it have, but its momentum, it’s ability to act like mass, changes. This is a really confusing concept, but the best way to think about it is if you have two observers. Both looking at the same event they need to see the same thing and since time changes based on how fast you’re moving; if I’m watching a train moving at close to the speed of light, it would be very hard for me to watch it, but ignoring that, I would see time for the people on the train slowly approach a stop. This means that if someone were to drop a really nice pot, it would appear to very slowly drift towards the bottom of that very quickly moving train. Now a very slow moving pot should just gently touch the ground, but the reality of it is, is that if it weighs enough when it touches the ground there will be no gentle about it, and it will shatter into a million pieces. It’s equivalent mass, its relativistic mass, it has to increase in order for it to shatter when it hits the ground, in this, I perceive time moving very slowly for the people on this fast moving train. Now at the same time, for the people on the train, it’s a normal pot, you dropped it, this sucker moves fast, the thing shatters into a million pieces. It’s because of this change in relativistic mass that we are both able to perceive the exact same shattering of the pot.

Fraser: So then let’s actually look at the formula itself, break it down bit by bit. Lets start with E, what’s E?

Pamela: Energy

Fraser: Energy, as measured…

Pamela: It’s the ability of something to do work if you rest enough of the bits out of it.

Fraser: So typically it’s measured in Joules? Megajoules?

Pamela: Calories

Fraser: Calories, okay that’s E then M?

Pamela: Mass

Fraser: Ok so that’s mass in kilograms, grams?

Pamela: yeah

Fraser: Ok, C?

Pamela: Speed of light, kilometers per second or meters per second depending on what you decide to use. The normal units are meters per second, mass in kilograms and energy in joules.

Fraser: and then you square the speed of light and that’s where it gets ridiculous, right? The speed of light is already 300,000 meters per second and then you square that number and you get whatever you…

Pamela: Well it’s 300 million meters per second, 300,000 kilometers per second. So you take 300 million meters per second, and square that sucker and, yeah that’s a large number. What’s neat about this is if you turn this equation around and look at it as a ratio instead, the energy tied up in an object divided by its mass is always equal to the speed of light squared and that’s just kind of cool.

Fraser: When you think about, as an example I have here a nice little iron meteorite.

Pamela: Hey I’ve got one of those too!

Fraser: I know, (Laughs) we all do, we all do. It’s a phil-plate meteorite, if he really likes you he’ll give you an iron meteorite. And so it’s like 40 grams or so but there is enough energy to power a city in this piece of metal.

Pamela: For a brief period of time, yes.

Fraser: Yeah it’s a phenomenal amount of energy locked up in all the matter around us, in fact its as if everything around us are bombs waiting to go off. ,

Pamela: Frozen energy?

Fraser: Frozen bombs but the trick is unlocking that energy, that’s the hard part. So lets get back to Einstein then. You already lead into it which is the Relativity concept, so how did Einstein come up with this idea?

Pamela: What’s interesting is that initially there was no E=MC^2 in his paper, it was kind of this sentence off to the side that, according to the translation of the German that I stole ruthlessly from Wikipedia, it said that if a body gives off the energy L in the form of radiation its mass diminishes by L/V^2. This has to do with how the momentum is effected in the process it has to do with the conservation of kinetic energy tying into everything. It was only later that Max Plank was the one who wrote that the mass that is initially in a system is equal to the energy initially in a system divided by C^2. It’s very important that you think of this in terms of mass and not matter because mass and matter are not really interchangeable. Matter is frozen energy, but when you have something, potato for instance; potato is everyone’s favorite example. That potato is made up of a certain amount of particles, and those particles are matter, they are tied to the Higgs boson, they have a mass because of that, but the amount of matter in it is a specific thing. The amount of mass is different and it’s hard to sort that out because you can pull apart an atom and depending on what it was when you started you still have the same bits, but the energy of the bits has changed and the mass energy is conserved and the matter is something different and you can actually, if you take a bunch of energy, you can turn it into matter but the mass energy is conserved.

Fraser: How did this even occur to him?

Pamela: He’s a genius?

Fraser: Well I understand that but you were saying this before that he was thinking about the implications of mass moving at relativistic speeds, that it being equivalent to energy had to be the outcome, right?

Pamela: It falls out of the equations naturally, that’s one of the disturbing things when you’re asked to do all these homework problems in general relativity and special relativity. This is one of those things that when you start looking at “how does momentum change as an object accelerates” and you take into account relativistic corrections. When you start looking at all these different things it just falls out naturally that you have this E/M=C^2 and that’s how it falls out naturally. It doesn’t fall out at E=MC^2 it falls out as the speed of light squared just happens to boil down to energy divided by mass.

Fraser: So back when Einstein first proposed this equation, you mentioned that the next plank had refined it, did Einstein come back around and give it its final form?

Pamela: Einstein did return to the topic. He did write E=MC^2 and was the title of one of his articles, but by the time he got around to doing it, it was already generally being used. That’s one of the great things about science, is, while it may take us a while to decide how we’re going to generally refer to things and what we’re going to name things; once that relationship is discovered, everyone uses it. In this case he wrote down a brief sentence and it got out and got written out, everyone started using it and he did get credit because he was the first to write it down but him writing E=MC^2 did take a little longer to get to.

Fraser: I guess, again, back when he first devised this, this was the beginning of the 20^th century, right?

Pamela: 1920’s and then he continued working on it through the two World Wars.

Fraser: Right, okay. They didn’t have a lot of practical applications or ways to even test this out that much?

Pamela: Well, in Astronomy we are starting to figure it out. What’s kind of amazing is that they did have to use all these sorts of things when they were starting to figure out the quantum mechanics of what drifts stars and when they were looking to figure out nucleosynthesis in stars. There are a lot of ideas that this influences. You need to have this energy idea that’s linking between mass and energy to start to consider nucleosynthesis, nuclear reactions, and nuclear bombs. It’s the foundations for a lot of very scary and powerful, and I mean that literally, powerful ideas.

Fraser: Right, so I guess you have the situation where the astronomers are like “We don’t know how stars work, we think they burn.” You can’t get that much energy…

Pamela: (Laughs) Well Evington had figured it out but we were still working on the details. Evington did some good work for us in the turn of the century, they’re all compatriots of each other.

Fraser: Right, but you’ve got a situation where you finally have a mechanism, you can finally understand what that mechanism is and what that relationship is. But I think where a lot of people really think about E=MC^2, they think about the nuclear program for WWII.

Pamela: Right and this is where, when you think of TNT, plastic explosives, when you think of most conventional weapons, you’re looking at a chemical reaction that when it takes place gives off huge amounts of energy compared to, like, mixing hair dye, which releases a small amount of energy, this is why they say tear the cap off of the hair dye before you mix it. Sorry if that was a little esoteric for all you men out there.

Fraser: You dye a lot of hair Pamela so we know why that’s on your mind

Pamela: I do dye a lot of hair, yes. So lots of chemical reactions give off energy. A lot of them also will take energy from their environment in the containered reactions going in will feel cold, but if a reaction is exothermic enough, energetic enough, it will release energy that actually shatters the chemical reaction going on. It releases so much kinetic energy into this system that things blast apart. But this is a chemical reaction, it has to do with the binding energies of the chemicals involved and that binding energy getting transformed into kinetic energy and thermal energy. With nuclear reactions you’re just taking the atoms apart and taking the energy of the atoms and releasing that and that’s a lot more powerful that just a standard chemical bond of whatever sort you’re dealing with. So now you’ve gone from the potato powering the, chemical means, a light for a science fair project, to all the energy in the potato poweringNew York City.

Fraser: So you really are getting that conversion of the mass into the energy of the potato.

Pamela: …the matter into the energy

Fraser: Yeah the matter into the energy where you actually blow up that potato at a nuclear level.

Pamela: Right and luckily, potatoes do actually resist this. But the other side of this, everyone thinks about the death and destruction and mayhem that you can do with nuclear weapons, and they look at the evil side of the equation. What’s kind of awesome is the converting energy into matter side of the equation. You and I are just frozen energy. We don’t think of it that way. But when our universe formed, our entire universe was nothing but energy and it took the universe expanding and cooling for that energy to finally be able to freeze out into matter, into protons, into electrons and neutrons came in eventually. There was early nuclear reactions and all of that was, a transformation process of nuclear energy into matter. Today in our quest to try to understand the particle physics world, we’re taking particles, electrons and protons, colliding them at high velocities inside of various types of accelerators depending on what we’re looking for and it’s in the energy of that collision that we look for particles that come out of that energy, the kinetic energy that’s transformed into something we may not have realized existed before.

Fraser: So what is the process? We talk about turning energy into matter and matter into energy, what is the process to, say, turn energy into matter, for an example? How can science do it now?

Pamela: Well it’s a matter of overcoming the forces in the center of the nuclei. Normally you have protons and neutrons in the center of the atom that are held together with “glue-ons”, because we are boring in naming the things that hold our atoms together, but at the same time they are repelling each other. This is the strange dichotomy, that causes atoms to get more and more unstable as they get larger and larger. Eventually when an atom gets too large it gets unstable and splits into something more stable. Now if you’re able to take and squish those particles together even more, you eventually overcome their ability to be stable and separate from one another, and in that moment of being crushed, they’re forced to become energy so you’re overcoming the nuclear forces inside the atom.

Fraser: Right, and how practically do they do this, say, in a nuclear reactor?

Pamela: Well in a nuclear reactor they don’t bother with the full atom. They strip it out to it’s simplest pieces, so you take two protons and collide them with so much force that in the moment they come together, the ability of the protons to repel one another, is overcome by the fact that they’re already flying together. That force of repelling doesn’t have time to slow the interaction enough and as they come together they end up converting into pure energy as they smash and they can no longer exist as protons.

Fraser: Okay. Its, again, almost the most efficient way to do this, the most efficient way is matter antimatter, but you had to have already built your antimatter in the first place right? Which is complicated.

Pamela: I’m not sure that there is any more or less efficiency in it, they’re just different. In both cases you’re releasing energy and it’s eventually freezing out as particles, but yeah, creating antimatter is a bear, and yeah, they’re just different.

Fraser: Okay so lets go the other way, lets go from matter into energy

Pamela: Well this is one of those neat parts that if you have a pile of energy hanging around it will naturally collapse into a particle and anti particle that have conserved momentum and fly off in opposite directions. This is something that’s going on all the time. There’s reactions ongoing on a regular basis where we have for instance beta decay and anti beta decay processes where neutrons break down into electron and anti electron neutrino conserving the momentum, conserving the charge, all the little bits. There’s all these conservationals that we have to pay attention to and one of the things people don’t seem to acknowledge is that there is anti particles everywhere, they’re generally anti neutrinos but they’re everywhere and a little bit of antimatter is not going to hurt you

Fraser: A little bit of antima… (laughs) Right? They use it for medicine right? They drop a little bit of antimatter in your body and watch as it explodes inside of you.

Pamela: (Laughs) No, they usually take a bit of normal radioactive matter that as it undergoes radioactive decays it does release beta particles and…

Fraser: I thought there was a form of it where they have, what was it? Positronic emission technology? Anyway, but the point of it is that scientists are using antimatter in their daily work these days.

Pamela: And we’re not blowing up the planet, it’s really not a concern. Antimatter exists, we’re not really sure why regular matter is the dominant one in the universe folks, we’re still working on it. The fact of the matter is that antimatter is everywhere, it’s just the minority form of matter, don’t hate on the antimatter.

Fraser: So there are free floating anti particles floating every now and then, and detonating?

Pamela: I think detonating is probably too strong a word.

Fraser: Annihilating, that’s the word isn’t it?

Pamela: So in general the anti neutrinos that are passing through your body they don’t want to interact with anything. They don’t want to do you any harm. They are the most antisocial of particles and so the probabilities that anything bad is going to happen; the probability that we could detect these suckers when we try is very low so we don’t need to be worried. And yeah, positrons happen too, they can do damage, this is why one should avoid radiation… but what’s a few neucleotides in one??

Fraser: What were the, sort of, moral implications of this equation? I know it caused Einstein a lot of, I don’t know, I think he was quite sad when he realized the implications of this technology, or of this equation and what it could be used for in terms of great destruction.

Pamela: That’s the thing: Science can be used for good and it can be used for evil and morality doesn’t often keep up with technology. There is always the question of dominance and humans like to be dominant over one another and here he was working to understand all the science that would lead to all of the positives: GPS. We have GPS because of relativity; understanding the formation of our universe is grounded in understanding relativity. But the other side of that was realizing exactly how fusion and fission can occur; realizing how to form hydrogen bombs and how to form nuclear weapons from plutonium and uranium, depending on your methods. It was this realization that we can cause runaway nuclear reactions if we trigger them correctly. That was the foundation of the Manhattan project during WWII and if it had only been used as a “Look at how big of a stick we have, now everyone be quiet and stop fighting” that would have been better, but the reality is, we dropped two bombs on Japan. I’m not going to argue the morality of that. I wasn’t alive, I haven’t studied it in detail. The reality is that we now live in a society that there is an ease of obtaining nuclear materials and it’s possible to conceive of the crazy intelligent suicide terrorist that creates the weapon in a suitcase. Luckily the technologies are hard to get a hold of, they’re extremely expensive to get a hold of but as miniaturization takes place, as technology drops in price we have to be concerned of the future where the suicide bomber isn’t carrying TNT or plastic explosives but the suicide bomber is carrying a dirty weapon and that’s a terrifying future and we can only hope to try and avoid it.

Fraser: Yeah, you can only imagine what they were wrestling with when they started to realize the implications of the math, of the physics, they were uncovering. Then on the one hand it was clearly possible to use this for great, you know, power plants and reactors and you can power ships and cities with this. They didn’t understand the waste issue with all this kind of stuff, but they could see it used for great good. Then on the other hand you can detonate these things and you are using them for great evil. How do you begin to communicate this to the politicians, because at the end of the day it’s just nature right? Reality says this all works…

Pamela: And it’s this horrible trade off. I’m a strong advocate of safe nuclear energy, the problem though is what is right and what is safe and what is good is often destroyed in the face of what is cheap and how do we make the most money. And because humans aren’t perfect there’s always going to be that person who looks at the trade off of probabilities. The “if we don’t spend this $100,000 there is a fractional increase in potential hazard”. And those sorts of decisions, the decisions not to spend the money for reprocessing, all of these decisions add up to a society that’s not ready to be fully responsible for nuclear energy. We live in a geologically unstable world and that requires even further expenditures and further risk and this is something thatJapanis struggling with greatly right now. It’s a small nation, it’s one of the most environmentally conscience nations in the world. They even tell you how to correctly recycle lipstick.

Fraser: Yeah, a special box just for the lipstick.

Pamela: It’s really something to be profoundly proud of. But at the same time they are such a small nation, they need nuclear energy. They’re a geologically unstable nation and they’re a technologically driven high energy demand nation and now they’re trying to struggle with “how do we balance the geological instability with the desire to not use coal or other chemical fuels that increase the carbon load on our atmosphere” and this is a “we have the technology, but don’t have the money, do we have the understanding” they are trying to balance all these different things. It always reminds me of Dante, just to bring in things from left field, he said the root of sin is not understanding the consequences of our actions and you have to wonder if the root of doing bad to our planet is not understanding all the scientific implications at work.

Fraser: Its amazing we’re still dealing with the implications of this discovery and I think that is just a short form of how to unleash this whole complex constellation of ideas all at the same time that it’s about death and it’s about WWII and it’s about the power and the risks and Fukushima and all of these things, all at the same time

Pamela: And it’s also about life, it’s about stars, it’s about origins of the big bang and it’s that dichotomy that as scientists, we always have to be concerned. What is it that we’re discovering? The area of the stars is a nice place to work.

Fraser: I think that was great, thank you very much Pamela and we’ll see you next week.

Pamela: My pleasure Fraser.

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

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

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