Planetary Radio: Space Exploration, Astronomy and Science - The Brightest Light in the Universe

Episode Date: April 28, 2008

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The brightest light in the universe, this week on Planetary Radio. Hi everyone, welcome to Public Radio's travel show that takes you to the final frontier. I'm Matt Kaplan. You had to be pretty swift to see that bright but short-lived light halfway across the cosmos. In fact, you had to be the spacecraft called Swift. We'll talk with Swift's

principal investigator, Neil Gerols, about his unique orbiting observatory and the brightest ever gamma ray burst it discovered barely a month ago. Bill Nye the science guy was blown away by the implosion of a star that caused that so-called GRB. He'll share his excitement with us in just a minute.

Later today, Emily Lakdawalla will explain why Saturn beats Big Brother Jupiter in the ring department, and Bruce Betts will join me on location for another what's-up look at the night sky waiting right outside your window. We'll also get more than our fair share of rodent acronyms in the space trivia contest. We are less than one month from touchdown of the first probe to visit the Martian Arctic. Emily's blog will show you the Phoenix landing zone at planetary.org. Ms. Lakdawalla is also sorry to report that Mars Exploration Rover Opportunity's

arthritic shoulder is acting up. One of several motors in the rover's arm may have failed. Engineers are analyzing the problem. Here's Bill Nye. Hey, hey, Bill Nye, the planetary guy here, Vice President of Planetary Society. This week on Planetary Radio,

the size of the universe. And it's big. It's really big. Recently, we observed what seems to be the biggest burst of light ever observed by humans. We're talking about a gamma ray burst. And when I say light, I mean it in the big sense. Gamma rays would be included with the visible rays. Now this object apparently is a star collapsing, collapsing so fast with so

much energy it becomes a black hole. And as this collapsing stuff releases its intrinsic oomph, it produces a burst of gamma rays in a beam. And this beam happened to be pointed at us. And we observed it with a satellite called, a satellite, a spacecraft called SWIFT. Now, if you watch the Bill Nye the Science Guy show, you may remember we interviewed some scientists who work on the Burst and Transient Source Explorer. This was a spacecraft built to observe gamma rays from space. And we observed not only that, we observed some gamma rays from thunderstorms. But along with this came the ongoing effort of building a spacecraft called SWIFT. And later in the show today, Neil Gerrills,

the principal investigator on this spacecraft, will tell you all about it. The red shift, so big that we figured out that this thing was seven and a half billion light years away. Seven and a half billion light years, people. That's far, far away. And it had two and a half million times the brightness of anything else we've ever seen, if only we'd been up close. Except then we'd probably have our DNA disrupted. But that's another thing. Neil will tell you about that, too. Stay tuned to Planetary Radio. Until next time, I've got to fly. Bill Nye, the Planetary Guy.

Bill just gave you a great introduction to our topic. I'll just let you know that our guest, Neil Gerrels, is very well qualified to tell us about these monstrous explosions called gamma ray bursts. Neil is principal investigator for the Swift spacecraft that Bill mentioned. It is far and away the best tool we've ever had for discovering GRBs, which were first found entirely by accident by satellites designed to monitor nuclear tests on Earth. Dr. Gerl's heads the Astral Particle Physics Lab at NASA's Goddard Space Flight Center in Maryland.

He's also a professor of astronomy at both the University of Maryland and Penn State. Neil, thanks so much for joining us on Planetary Radio. My pleasure. We don't often on this show look halfway across the universe for topics, but this one was just too bright for us to ignore. This find that you got on March 19th, quite a big deal. That's certainly the brightest gamma ray burst we've ever detected, and it's the brightest object in the sky of any astronomical type. It was like a magnitude 5, which I guess, if you'd been looking in the right direction,

I don't know about from a city environment, but you could have looked out naked eye and seen this object, at least for a few seconds. That's right. In a dark sky, in a dark sky, the eye can see to about six or six and a half magnitudes. And magnitudes are backwards, so the smaller number, the brighter. So this one would definitely have been visible to the naked eye. Unfortunately, nobody was actually looking at the time, and it was only that bright for a few minutes.

So one would have had to run outside and look, but it could have been seen by the naked eye. Well, fortunately for all of us and for science, your spacecraft was watching because it's always watching. Swift, that aptly named craft that you are the principal investigator for, noticed this and I guess swung right over. That's right. Actually, it's one of the few NASA spacecraft that is not an acronym. The word Swift because we rapidly rotate. And we're always looking at the sky. We're looking primarily for gamma-ray bursts.

That's what the satellite was designed for. But we see other transient objects in the sky, and we slew to them. So we have a wide-field instrument that's looking in the gamma ray part of the electromagnetic spectrum. And when it sees a flash like this, we calculate the position on board, and the spacecraft within about a minute rotates and points other telescopes in that direction. Before SWIFT, did we simply miss a lot of GRBs because we just couldn't get to them fast enough? Yes, we missed a lot. And there were previous satellites that have detected gamma-ray bursts and detected even large numbers of gamma-ray bursts. But in those cases, without the rapid slewing and observations

with more angularly precise telescopes, they weren't able to locate them on the sky. For those previous observatories, we never knew exactly where they were coming from and had trouble understanding what caused them. Can you give us an idea of just how much brighter this particular burst, GRB 080319b, how much brighter it was than anything else we've ever seen? Well, we have seen some other bursts that were fairly bright,

but this one was maybe a factor of 1,000 brighter than any of those that we've even seen with our own satellite. So one thing I should point out here is that first there's a gamma-ray flash for these. That's why they're called gamma-ray bursts. And then afterwards, there's an afterglow, both in the X-ray band and the optical, sometimes as seen in the radio band. And so by the brightness, we're talking about that optical afterglow emission that's seen after the burst. But most of the energy, I bet, was in the gamma rays.

Yes. For a burst like this, there's a fairly reasonable fraction, you know, between 10 and 50 percent that's in the afterglow part of the burst. But we learn a lot by observing the optical and x-ray afterglows because we can study those with beautiful, high-precision telescopes that can image them and study them in detail. This was so much brighter, as you said, by the factor of 1,000. That was obviously what made it visible across such a huge expanse of space. I read that prior to this, the brightest object that could have been seen, I guess, naked eye from Earth, was a galaxy that was maybe 1,300th as far away. Yes, that's right. That's M33. That's a bright galaxy, but it's fairly nearby in cosmological terms. It's only millions of

light years away instead of this one, which was seven and a half billion light years away. There are apparently two types of gamma ray bursters, and I guess current theory says there may be different progenitors, different reasons why these take place. We actually didn't know that before the Swift mission was flown. We had been observing only one type, which was the long gamma-ray burst. The names have to do with how long they last, and the division point is about two seconds. So long gamma-ray bursts last some tens of seconds. They're already, even in the late 90s, some indication that they're due to the explosion of stars, but not like a supernova, a normal supernova explosion.

But these are stars where the core of the star collapses to a black hole. When that happens, there's a huge gravitational pull in the center of the star, and jets of material come streaming out that cause the gamma-ray burst. So that's the long class. This one we saw on the 19th, by the way, was a long gamma-ray burst. But the ones that are shorter than two seconds, we've found to have a very different origin. They're probably caused by an orbiting pair of neutron stars,

which are dense, compact stars. And as they orbit, their orbital distance slowly decreases. They come closer together and finally merge in a fiery explosion, which interestingly also produces a black hole. And we think a gamma-ray burst. But it's a very different way to produce a black hole. Do we have theory that can actually tell us why such an enormous amount of energy is created in either of these types of cataclysmic events? It actually occurs very naturally. And before there was even these observations showing the short bursts being associated with merging neutron stars,

theorists had predicted that that kind of coalescence of compact objects would produce a gamma-ray flash. And the reason is that there is so much gravitational energy that's released when these small but very massive objects join with one another. So they're powered by gravitational energy. And if you do the math, you can figure out how much energy would be released. And it's the kind of energies that we see in gamma-ray bursts. That's Neil Gerrold's principal investigator for SWIFT, the orbiting observatory that watches for gamma-ray bursts. More of Neil when Planetary Radio returns in a minute.

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That's planetary.org. The Planetary Society, exploring new worlds. Welcome back to Planetary Radio. I'm Matt Kaplan. Gamma ray bursts are the biggest releases of energy we've ever discovered, and we're seeing many more of them thanks to SWIFT. Neil Gerrolds is principal investigator for SWIFT, an orbiting observatory that detects GRBs and, in less than a minute, turns its instruments toward these powerful but brief explosions.

SWIFT did just that on March 19, when it found what turned out to be a GRB that dwarfed all others previously seen. Do we have an idea why this particular burst, 080319B, was so particularly powerful, so much more powerful, than other bursts we've seen at least to date? It's an active area of investigation right now, and I don't have a good answer why this one, you know, why one of them is so much brighter than the other.

The total amount of energy released in the center of this star when the black hole is formed may be fairly much the same from object to object, but somehow the fraction of that energy that goes into these streams of particles coming out seems to be very different. And so you can have a gamma ray burst at the same distance, two of them at the same distance, one of which, you know, may be a one thousandth or even one hundred thousandth as bright as the other. There's a very broad range.

This one was an exceptionally bright one. We don't catch all of them, so we were lucky to catch it with the Swift satellite. You don't want to get too close to one that's underway. That's true. If one happened in our, even in our own galaxy, this one would have been brighter than the sun. So, you know, that's pretty bright, but not too scary. If it had happened within the region of our galaxy near the Earth, let's say within 1,000 light years or so,

then it would have been so powerful as to essentially damage or even blow off the ozone layer of the Earth and certainly harm life. Luckily, the probability of that happening is extremely small. So it's not something we have to stay awake at night about. I read the GRBs, an approximate rate for these might be one per galaxy per 100,000 years. Is that correct? Yes, it's something like that. And again, there's a very large uncertainty on that.

It could be as infrequent as one per galaxy per billion years or perhaps 100 million. But that is the kind of timescale that planets can evolve life. And so if you think about it not in terms of our own Earth as a hazard, but in terms of every time a gamma-ray burst goes off, it's in some galaxy, and there are many planetary systems and many stars around it. So they are a very powerful effect on their own environment. What do you think of those who have hypothesized that the great dinosaur extinction event on our planet may not have been a meteor strike,

but a GRB that went off a little bit too close. Personally, I think that the, you know, Ordovician extinction, one of the extinctions, may have been caused by a gamma-ray burst, but not all of them. And the big extinction 60 million years ago that did away the dinosaurs seems to me anyway to be better explained by an asteroid or meteor strike. We do have that convenient iridium layer, and I guess nobody has pointed to evidence of a GRB having taken place at the right time and place. Yeah. Let's turn back to this spacecraft, which I just remembered, I think I read, that your mission has been extended. First of all, it's going to be in orbit till 2020. So it'll be around for a long time. There

are no rockets on board. There's no way that we can bring it back in. And we'll be operating as long as our hardware lasts. So far, it's working well, knock on wood, and as long as we can keep getting NASA funding. But it's been extended through 2010, and just now we've been presenting a proposal to NASA to extend it beyond that. And when you say we, this is a team from around the world. It's an international team. We actually have 200 scientists on the SWIFT team. Maybe about 30 of them are active and operating the satellite any day.

But there are many others that, for instance, have ground-based telescopes that follow up the births or that are involved in other aspects of the mission. Primarily in the U.S., but there are quite a number in the U.K. and Italy. Those are partnering countries that provided some of the telescope hardware on the spacecraft. partnering countries that provided some of the telescope hardware on the spacecraft. I neglected to mention, or we neglected, that another of Swiss functions is not just to do its own, collect its own data, but to alert everybody down here on Earth, like those Earth-based astronomers you mentioned.

Yeah, it's kind of fun. It's like a beacon coming from space. Whenever a burst goes off, we don't know within a few seconds that this has happened. We have a pretty good position on the sky within that time. So we send that position down to the Earth, and it goes out on the Internet. Anybody can subscribe, actually. But primarily, these ground-based telescope teams subscribe to that. And some of them actually have telescopes that automatically repoint whenever they get a message from us. We're just about out of time. Let me turn back to March 19 for a moment,

because this one largest of all bursts ever seen was one of only four that day. Was that unprecedented? It was absolutely unprecedented. In fact, sometimes we think that the cosmos is conspiring against us, but it seems to just be statistics. We had just before that time, in December and January of this last year, gone through six weeks without a single gamma-ray burst. We usually detect two a week. Four in one day was a statistical fluctuation in the other direction.

It was just a very large number. And it was actually the second one out of the four that turned out to be this real whopper. Now, I've also heard that it was just the cosmos wanting to honor the passing of Arthur C. Clarke. That's true. He died on that same day. And we made mention of that in our press coverage about the burst. Yeah, that was the first place I saw it, and we ran a tribute. We are out of time. I want to thank you very much for joining us to tell us a bit more

about these most energetic of all explosions in our universe, ignoring the Big Bang itself, of course. And I'm glad to hear that you're going to continue to be on the lookout with Swift. If you find a bigger one or one that's just as interesting, I hope we can talk to you again. I enjoyed talking with Swift. If you find a bigger one or one that's just as interesting, I hope we can talk to you again.

I enjoyed talking with you. Thank you. Neil Gerols is the principal investigator for the Swift spacecraft on the lookout for gamma ray bursts and other large events of that type taking place around our universe, even if they happened seven and a half billion years ago. He's also the chief or head of the Astroparticle Physics Lab at NASA's Goddard Space Flight Facility and a professor of astronomy at the University of Maryland and at Penn State. We're going to be back with another astronomer. That'll be Bruce Betts for this week's edition of What's Up after we drop in on Emily. Hi, I'm Emily Lakdawalla with questions and answers.

A listener asked, Why does Saturn have more rings than Jupiter when Jupiter is much bigger in size? The complex system of rings that surround Saturn is larger, broader, and more massive than the rings around any of the other giant planets. In order to explain why Saturn's ring system is so large, we need to know how the ring system formed in the first place, and experts are still debating that question. One point of agreement among scientists is that rings probably formed when moons were shattered. scientists is that rings probably formed when moons were shattered. Most of Saturn's icy moons have giant impact basins, and it's not much of a stretch to think that there are moons that we're not seeing because they were hit with such large impactors that they were blown to smithereens. It actually wouldn't take a very big moon to make Saturn's enormous ring system.

The rings are large, but they are incredibly flat. If you took all the ring particles and squeezed them into a ball, you'd wind up with a rather small icy moon between the sizes of Mimas and Enceladus. So Saturn's ring system may be just a happy accident. Saturn may have had a moon of just the right size and in just the right place that an impact smashed it into the beautiful ring system we see today. Jupiter, by contrast, may have been unlucky. Either it didn't have a large enough moon within its Roche limit, where the planet's gravity would prevent smashed up moon pieces from re-coalescing, or its moons were too big and never got hit by anything large enough to shatter them.

Scientists aren't even sure if Saturn's rings are old or young, but the fact that all four giant planets have at least some rings suggests that Saturn has always had them too. Got a question about the universe? Send it to us at planetaryradio at planetary.org. And now here's Matt with more Planetary Radio. From the Pasadena Hilton in, well, of all places, Pasadena, California, it's time for What's Up with the Director of Projects for the Planetary Society, Bruce Betts. Why in the world are we in this big empty room? Well, we've snuck in just so we can feel what it'll be like in another month or so. On May 25th, when Planet Fest 2008 rocks your world and Mars, too.

New visions of Mars. The cold helps. That does. You get a very nice low voice with that cold you got going. Thank you very much. Yeah, so we'll be having Planet Fest, new visions of Mars here in this big empty room You get a very nice low voice with that cold you got going. Thank you very much. Yeah, so we'll be having Planet Fest, New Visions Mars, here in this big empty room that hopefully will be a big room filled with lots of people,

looking at a big giant screen that will show live the Phoenix landing, and we can all celebrate, or mourn, together. Don't say that. As a group. Trust me, if I were a jinx on spacecraft, I would have killed several by now since I'm always skeptical. But, you know, things look good for them. They're in good shape. So here's hoping.

But in any case, that's what's exciting about Mars landings is they are exciting. And you don't know what's going to happen. And it's hard to do. It's really, really, really hard to land on Mars. But if you do, it's really cool, and this will be a really cool, totally new place. First attempt at the first landing in the polar region. So it should look a lot different than what we've seen at the other landing sites. And we're going to have a heck of a party here on May 25th. It's going to be real fun as we wait for that moment when Phoenix touches down.

And you'll get more information on PlanetFest on our website, planetary.org. And you can consider coming. There are also some affiliate events around the country, a little less so around the world. Right now it's up in the night sky. Indeed, Mars is up there in the evening sky. It's a lot smaller and dimmer than Phoenix is seeing it right now. But you can see it in the east, high in the east in the early evening. Getting dimmer, dimmer, but still a cool red object still up there above Orion.

High in the east is Saturn, really close to Regulus in Leo. And it's looking yellowish and always lovely, of course, in a telescope. Check out the rings. Check out Titan off to the side. And in the pre-dawn sky, Jupiter getting higher and higher. Can't miss it. Bright star-like object over there in the east. That's our night sky, morning sky roundup.

Okay, what else you got? I've got random space fact! I may not even have to add echo. That was not bad. That's the best since the racquetball court. It's true. It's true. Great and strange moments in planetary radio history.

On to Titan. Big, huge moon of Saturn. And Titan's interesting, of course, because it's the only moon with a significant atmosphere. Interesting because it's a nitrogen atmosphere, just like Earth is dominated by nitrogen. Interesting because it has an atmospheric pressure at the surface even higher than Earth. But here we get to the real random space fact. Because the gravity is so much lower, it's so much smaller than Earth, the atmosphere extends much, much, much, much farther than it does on Earth.

It's like six, seven times higher, depending on how you measure it, even though you've got a similar pressure, you know, within a factor of two at the surface of the object. So tight. That's a good one. Good fact. Hey, thanks. Let's go on to the trivia contest. Now, I asked you what many probably felt was an easy question, but as always, I like to mix them up a little easy, a little hard, a little rodent. And so this time we went rodent, and I asked you what is the most rodent-like instrument on the IDD, the instrument deployment device on each of the Mars Exploration Rovers. How'd we do, Matt? Yeah, it was a little easy. We were inundated, and so let's just go right to it and tell you who won. It was Tom Hannon, first-time winner from Blackheath, London.

That's the UK, of course. Tom, congratulations. He did indeed say, we were looking for the rat, the rock abrasion tool. That is indeed the answer. Did we get any other, you know? Oh, did we? Did we?

Like, you don't know. We got a bunch. You know, we can't possibly go through all of these, and we do apologize because some of you were so creative. But it was both quantity and quality. We're going to talk about John Lease. He came up with all kinds of wonderful new acronyms that are not on the rovers, but he says are the mouse, the gerbil,

the hamster, the capybara. That's my personal favorite, you know, largest rodent in the world, and he actually managed to work an acronym out of it. Now, you want it? Here it is. Composite Alpha Particle Y-Band Aperture Radio Antenna. By the way, this is not an official acronym from the Mars Exploration Rovers. John, you're going to be hearing from the NASA Office of Official Naming. Yes, no capybaras on the spacecraft. They're too massive. We did have several people who came up with this,

one of them being our usual funny guy, Torsten Zimmer. Not the Mausbauer spectrometer, but the Mausbauer spectrometer. Pretty good. That is pretty good. Well, should we give them another trivia contest? Yeah, can we? I'm thinking. Yes, we can.

I got a question for everyone. That's kind of how this works. What was the first spacecraft to pass 80 AU, 80 astronomical units from the sun? We've got some out past that now. What was the first to pass 80 AU, astronomical

unit? Of course, the average distance between the Earth and the sun, 80 AU puts you like twice as far out as the planet formerly known as Pluto. So go to planetary.org slash radio, find out how to enter, and compute for a Planetary Radio t-shirt. If you have the correct answer and are randomly selected, when do they have to get that in by, Matt? They got to get it to us by the 5th of May, May 5, 2008, 2 p.m. That'll be a Monday, 2 p.m. Pacific time. And you might win yourself a Planetary Radio t-shirt.

Hey, Matt, you think one of these big giant chandeliers would look good in my place? Yeah, right next to the capybara. Hey, he needs a reading light. Say goodnight, Bruce. I mean, they've got big brains. They're big old hanging... All right. Thank you, everyone.

Go out there, look up in the night sky, and think about your favorite rodent. Thank you, and goodnight. He's Bruce Betts. He's dimming the chandeliers here in the big room where we're going to celebrate Planet Fest in about a month. Phoenix, Phoenix, Phoenix. Landing, landing, landing. He's the director of projects for the Planetary Society, to celebrate Planet Fest in about a month.

He's the director of projects for the Planetary Society, and he joins us every week here. Well, not exactly here, but he joins us for What's Up. Planetary Radio is produced by the Planetary Society in Pasadena, California. Have a great week. Thank you.