Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
Transcripts

"Death Star"

PBS Airdate: January 8, 2002
Go to the companion Web site

NARRATOR: Peering into the depths of space, astronomers glimpsed something astounding, the most powerful explosions since the creation of the universe.

DON LAMB (University of Chicago): There's just nothing we know of in the universe that comes anywhere close.

NARRATOR: Explosions that released more energy than ever thought possible.

DALE FRAIL (National Radio Astronomy Observatory): This is the kind of energy you need if you took the mass of our sun, our sun, and turned it into energy into ten seconds, pure energy, E=mc2

NARRATOR: Their deadly radiation flared through entire galaxies. What would happen if such an event took place near Earth?

STAN WOOSLEY (University of California, Santa Cruz): It would be sort of like Hiroshima going off all over the world all at one time.

NARRATOR: For decades scientists have searched for the cause of this phenomenal violence. What is the source of these explosions that go back to the dawn of time itself?

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

Science: it's given us the framework to help make wireless communications clear. Sprint PCS is proud to support NOVA.

This program is funded in part by the Northwestern Mutual Foundation. Some people already know Northwestern Mutual can help plan for your children's education. Are you there yet? Northwestern Mutual Financial Network.

And by the Corporation for Public Broadcasting, and by contributions to your PBS station from viewers like you. Thank you.

NARRATOR: July 1967: An American satellite is on the lookout for nuclear blasts coming from the far side of the moon. It sounds like the plot of a Cold War thriller, yet with Russia and America locked in an arms race the U.S. military perceived a very real threat.

Seven years earlier, both countries had signed a treaty forbidding the testing of nuclear weapons. But with Russia able to send rockets into space, the U.S. feared the Soviets had a way to cheat.

RAY KLEBESADEL (Vela Satellite Program): The possibility of hiding a test in outer space afforded Russia an opportunity to gain an advantage. And the United States had no means to determine whether a clandestine test was being performed.

NARRATOR: The Americans knew that if the Russians detonated a bomb in space they could hide the initial explosion behind a shield or even the moon itself. So the U.S. military set out to design spy satellites that could pick-up traces of a blast that could not be hidden.

The satellites would search for the most long-lasting radiation emitted by an atom bomb, gamma rays.

A nuclear explosion doesn't just produce a bright flash of visible light. It generates radiation across the entire electromagnetic spectrum. A powerful pulse of long-wavelength radio or microwaves can destroy electronic circuits. Infrared heat radiation can trigger flash fires.

Then there are the wavelengths shorter than visible light. Ultra-violet radiation and X-rays can lead to cancer. But the most deadly of all are gamma rays, emitted by the expanding radioactive cloud that remains long after the visible light of a nuclear explosion has faded.

If the Soviets were violating the test ban treaty the American satellites would pick-up the gamma rays.

For two years engineers at a top-secret laboratory at Los Alamos worked on the satellites. Soon they were ready for launch. Code named VELA—Spanish for 'watchman'—they hunted in pairs, searching for gamma rays. On July the 2nd 1967, they got their first bite.

RAY KLEBESADEL: It consisted of two bursts and was reproduced very accurately between the records of the two spacecraft. Clearly it was something of interest; on the other hand it almost as clearly was not the response to a nuclear detonation.

NARRATOR: The satellites had recorded thousands of bursts of radiation, but nothing came close to the brightness of these gamma rays. They must have been produced by a violent explosion. If a nuclear bomb wasn't responsible, then what could have triggered them?

Solar flares erupting from the sun can shoot out intense gamma rays. Other high-energy events in the universe might also produce this radiation. But Ray Klebesadel could find nothing to coincide with the gamma ray bursts he detected.

Another twelve were discovered, and according to the VELA satellites, they came from random directions around the Earth. For years the mysterious bursts were known only to the scientists at Los Alamos. By 1973, it was time to share their existence with the world.

DON LAMB: It was a couple of months after Ray Klebesadel and the scientists at Los Alamos had announced their discovery and so I went on out there, met Ray, and learned all about the bursts.

NARRATOR: Like many of his colleagues Don Lamb, marathon runner and astrophysicist, was perplexed.

DON LAMB: I knew it was a mysterious phenomenon, but I think no one, certainly not myself, realized at that time what the depth of the mystery really was.

NARRATOR: The bursts of gamma rays were unlike anything else known to astronomers. They lasted only a few seconds and were difficult to locate. It took weeks to pinpoint their direction, and when astronomers looked all traces had disappeared.

DON LAMB: So it would be like you're in a darkened...completely darkened room and you see, you know, a flash over here unexpected...from an unexpected direction, then a flash over here, then maybe one in this direction and then over here. And after the flash was gone you'd look with the most sensitive telescopes, whether from the ground or from space, and try to see something, and you could never find anything that you could be sure was associated with that flash, with that burst.

NARRATOR: The bursts were so elusive, that many astronomers were unwilling to devote time to studying them. There were exceptions. Jerry Fishman and Chip Meegan were two of the first astronomers to take a serious look at the bursts.

JERRY FISHMAN (NASA Marshall Space Flight Center): The early data for gamma ray bursts were so sketchy. And gamma ray bursts can be produced by any one of a variety of things so that almost anything goes and you get all kinds of crazy ideas.

The National Enquirer thought that maybe we were seeing alien civilizations warring with each other and throwing nuclear explosions, nuclear bombs at each other. We really couldn't refute that. Nobody could refute that. They even got some respectable scientist to say, "Well, yeah, I guess that's a possibility."

RAY KLEBESADEL: I complained that that wasn't at all what I said, but nevertheless, it got published in just the form he read to me.

CHIP MEEGAN (NASA Marshall Space Flight Center): I got a phone call once from a guy who said that he not only knew what was causing the bursts but how to stop them. And I just said, "I've got to go to a meeting now."

NARRATOR: Whatever was creating the bursts, it was difficult to see. But Don Lamb and other theorists knew of an object that might just fit the bill.

DON LAMB: I was one of the first people to put forward a model about gamma ray bursts. And my first instincts were that they might be coming from neutron stars.

NARRATOR: Shining throughout the universe are huge stars some ten times the mass of our sun. When one dies, it dies violently in a brilliant explosion called a supernova.

It blasts away most of the star, leaving just a tiny core of dense nuclear material, a neutron star. Into this sphere just a few miles across is crammed the mass of two suns. The density creates incredible gravitational energy that might, under some circumstances, trigger gamma ray bursts.

DON LAMB: There were even ideas that perhaps neutron stars had comets orbiting around them, just like the sun does, and occasionally a comet actually crashes into the sun. And the idea was, here,perhaps, some material could fall onto the neutron star and it would hit the neutron star at a third of the speed of light because the gravity was so strong and produce an explosion.

STAN WOOSLEY: Another of the favorites, was the neutron-star-quake model—something quite popular here in California—that the neutron's star crust might crack in something resembling an earthquake, but because the gravitational field of the neutron star is so powerful, the energy released in a quake can be enormous. And so there were all sorts of variations that involved getting energy out a neutron star.

DON LAMB: One might say it was a golden age of theories in gamma ray bursts because the constraints from the observations were so sparse, were so limited, that it gave free reign to the imaginations of theorists in this era.

NARRATOR: But without more data, there was no way to prove any theory. Fishman and Meegan went searching for more bursts.

JERRY FISHMAN: The first instruments that saw these gamma ray bursts were very small. We knew if we could put together even a simple detector system but make it big that we had a good chance of seeing many of these gamma ray bursts on even an eight or ten hour balloon flight.

NARRATOR: They sent their detectors to the edge of our atmosphere to see if they could discern a pattern in the blasts.

Our galaxy is a flattened disc and Earth lies at its edge. When we look up at the night sky, we see it as a band of bright stars, the Milky Way. If the bursts were created by neutron stars in our neighborhood Fishman and Meegan expected to see them coming from the direction of the Milky Way. In the end they found only one and it wasn't where they expected.

JERRY FISHMAN: If the gamma ray bursts were in the galaxy, you would expect most of them to be right along the plane of the Milky Way within the galaxy.

CHIP MEEGAN: Even the weak ones.

JERRY FISHMAN: Especially the weak ones. And this one was one of the weakest ones that was ever seen and yet it was out of the plane. It caused us some puzzlement but not enough to really come to any conclusions.

NARRATOR: As more gamma ray bursts were located, they too came from random positions around the sky. Most astronomers believed they simply weren't seeing far enough into our galaxy to detect the full extent of the Milky Way. But one man thought the bursts were further than they could possibly imagine. Bohdan Paczynski thought everyone was thinking small.

BOHDAN PACZYNSKI (Princeton University): When I was first interested in gamma ray bursts they were generally believed to be in our galaxy. However, the single, most clear evidence of them being in our galaxy, our Milky Way, was missing. They were not seen against the Milky Way. They were everywhere, all over the sky. And that left just two possibilities: either they were very, very close to us, so close that the Milky Way was too far away to be seen, or just as well, they could have been very, very far away. And that's what I decided to go for.

NARRATOR: Paczynski's point was simple: although objects in our galaxy tend to cluster along the Milky Way, those that are farther away will be seen equally in all directions. So if the bursts were coming from distant galaxies they would appear randomly distributed across the sky.

BOHDAN PACZYNSKI: So a natural suggestion is that gamma ray bursts were coming to us from so-called "cosmological" distances, which basically means huge, huge distances—from the far end of the universe, you could say.

NARRATOR: But that posed a problem. The further away the bursts, the more powerful they had to be to reach us. And for them to come from the edge of the universe invoked energies beyond what a neutron star could produce.

STAN WOOSLEY: Is it a billion times further away? Must not be a million, must be about a hundred million.

NARRATOR: The kind of energy that still leaves astrophysicist Stan Woosley staggered.

STAN WOOSLEY: Even in the models that had gamma ray bursts in our own galaxy we needed things that were a million times more luminous than the sun. But in order for them to be a million times further away, as the cosmic models would require, the luminosity would need to be more like a billion, billion times the luminosity of the Sun.

This energy problem put Bohdan Paczynski out on a limb.

BOHDAN PACZYNSKI: If you had a crowded field in one part and complete emptiness in the other, I would rather go for the uncrowded area. But there is a price to be paid. If you are in the sufficiently uncrowded area you may look like a crackpot. And indeed, how do you know that you are not a crackpot?

NARRATOR: Fishman and Meegan went hunting for gamma ray bursts again, this time with the largest space telescope ever built, the Compton Gamma Ray Observatory. The gamma ray detectors on board were the most sensitive ever designed. If there were a burst anywhere in the universe, the Compton would find it.

JERRY FISHMAN: About once a day it would see a tremendous flash of gamma rays and it would show up in three or four or sometimes more detectors.

NARRATOR: The results were clear—one hundred and seventeen bursts scattered all over the sky outside the Milky Way. Fishman and Meegan were stunned.

JERRY FISHMAN: We knew that it had major implications for a lot of theorists that had been working on the puzzle of gamma ray bursts over the previous 10 or 15 years, and that this would throw out a lot of their theories, so we really wanted to proceed cautiously.

CHIP MEEGAN: Turn that whole thing upside down, sort of the old slogan that everything you know is wrong.

JERRY FISHMAN: That's right.

NARRATOR: When the news was announced it was a moment of triumph for Bohdan Paczynski.

BOHDAN PACZYNSKI: That was for me quite an emotional experience. To see 50 percent of people instantly accepting the obvious consequences and saying, "Okay, we goofed for ten years. Now we decided the data is unambiguous. Bursts are at cosmological distances." That was sort of rationale for me.

NARRATOR: But his triumph was diminished by the lingering resistance to his big idea.

BOHDAN PACZYNSKI: What was truly amazing was another 50 percent of the audience was unmoved.

STAN WOOSLEY: It took me and the rest of the community a while to get used to the idea that the bursts just weren't going to follow a galactic distribution. By 1993, I'd say the handwriting was on the wall. And so it was getting very hard to hold on to the neutron star model.

NARRATOR: Now astronomers found themselves in a quandary. It seemed probable that the bursts were coming from far across the universe. And if this were true, neutron stars could not explain them, for they couldn't generate enough energy to send gamma rays across such vast distances.

As many astrophysicists looked for other explanations Don Lamb searched for a way to hold on to his ideas about neutron stars.

DON LAMB: Look, we know objects, neutron stars, that produce bursts almost exactly like this—not completely but almost exactly like this. We're just lacking a population of those neutron stars which could account for the sky distribution.

NARRATOR: Don Lamb reasoned that if there were a population of neutron stars in a halo surrounding our galaxy, then that might account for the random pattern of bursts seen by the Compton. But whether astronomers believed the bursts were close by or coming from far away, no single theory made complete sense.

DON LAMB: When you're on the very frontier of science everything's chaos, confusing. You have one observational result that completely conflicts with another observational result and each scientist is using their own experience, their own intuition trying to figure out, "How much am I going to weight this result which clearly conflicts with this one?"

NARRATOR: The more scientists found out about gamma ray bursts, the more intrigued they became. Don Lamb and others needed a way to prove their theories right or wrong. News was spreading fast that the mysterious bursts were coming from beyond our galaxy. They were far more powerful than anyone had imagined, and astronomers began to see them as a cosmological sensation.

For twenty-five years a small group had had the field to themselves; now others were joining the hunt. Dale Frail had access to the largest radio facility in the world, the Very Large Array.

DALE FRAIL: There was an established community of people working on this problem for a good 20 years. I'm a radio astronomer. I work at the other end of the spectrum. So I felt that I had something to contribute that was unique and distinct from what they previously had done.

NARRATOR: It was now obvious that the bursts were randomly distributed across the sky. But how far away were they? The distance was critical because the further away they were, the more powerful they had to be to reach us. If the bursts were coming from the outer limits of the universe, then the forces that created them would be truly stupendous. Surely such violent explosions would leave a trace, a lingering afterglow.

DALE FRAIL: The afterglow idea is very simple. You release a large amount of energy there has to be some glowing embers left over of that explosion. We were looking for the aftermath of that explosion so we had very much, as radio astronomers, an idea of how to go about doing that.

NARRATOR: The key to solving the riddle of the bursts was to catch an afterglow.

STAN WOOSLEY: The reason we really wanted to do that, to find the counterpart, the object that had made the gamma ray burst, was that maybe we could out find how far away it was. We didn't know whether these firecrackers were going off next door or out in the comet cloud or in the halo of the Milky Way or at the edge of the universe.

NARRATOR: But in 25 years, no one had ever caught an afterglow. They must be fleeting. Astronomers needed to train their telescopes at the bursts much more quickly. They pinned their hopes on an explorer satellite called HETE.

DON LAMB: So the key ideas about the High Energy Transient Explorer, HETE, were that it would very accurately pinpoint the locations of the bursts and then share that with the community in near-real-time.

DALE FRAIL: So they'd detect the gamma ray burst and then they could give us a position accurate enough to point our very best telescopes at that position, so we could bring out our big guns if you like.

NARRATOR: After years of arguing over the origin of the bursts, astronomers thought HETE was the tool they needed to end the debate.

In November 1996, HETE took off from an airbase in Virginia. To the dismay of HETE scientists, NASA insisted on deploying the satellite from a Pegasus rocket strapped to the belly of a converted airliner. In previous launches, the Pegasus rockets had suffered a 40 percent failure rate.

DON LAMB: We said, "Look, we've spent a decade designing and building the satellite and now you're asking us to take a launch on a rocket that's shown, so far, to be very unreliable." And the answer that came back from NASA was, "You either take this ride now, or we close the program."

[On Tape] Peg is go. Peg is go.

DON LAMB: So the moment came when the aircraft, you know, says, "On my mark, launch. Three, two, one..."

[On Tape] Three, two, one...Drop.

DON LAMB: The rocket, it just dropped from the aircraft. And your heart's pounding and you're waiting because it will only ignite five seconds later. So you're counting to yourself.

[On Tape] Pegasus is away. Standing by for ignition...and Pegasus is up and burning.

DON LAMB: Ah, wow. You know that the first stage is ignited and it's headed for orbit so everything was going well and we were hearing, "We have first stage burnout."

[On Tape] ...burnout in approximately...now.

DON LAMB: "We have second stage separation. We have second stage ignition." And everything, all the telemetry...and you hear all these voices, of all the mission controllers who are monitoring and telling you how things are going. And we had third stage separation and just as that happened I just caught some person in the control room said, "We have an anomaly in the third stage bus."

[On Tape] This is Pegasus launch, stat. It looks like the transient bus has gone down. The transient bus has gone down.

DON LAMB: The other people in my office didn't understand what was going on, so they were still excited, and yet I was starting to feel this dread that something was terribly wrong.

[On Tape] ...and we appear to have a problem in the electrical system that fires the pyrotechnics that separates the spacecraft from the third stage.

NARRATOR: A flat battery prevented the payload doors from opening. HETE was in orbit and fully operational, and trapped inside the rocket.

DON LAMB: They could tell that HETE had turned on and was inside the canister...couldn't get out...but had tried to extend its solar panels and tried to turn and orient itself to the Sun. It was horrible. It was like HETE was in its coffin and it was struggling, trying to get out and there was really no hope of it.

NARRATOR: Buried alongside HETE were Don Lamb's hopes of proving exactly where the bursts were coming from.

DON LAMB: I really thought that there was a very good chance that HETE might break open the mystery and tell us really what was going on.

NARRATOR: But on the other side of the Atlantic, another team had joined the hunt for an afterglow, and they didn't need HETE. Paul Groot and Titus Galama were young, ambitious astronomers from the University of Amsterdam.

PAUL GROOT (Harvard University): It's a scientific curiosity, you know? There is this problem which has been there for 30 years, and...but we just came into science basically. And of course you're full of enthusiasm and you want to see, "Okay, let's have a go at this and see if we can crack this nut."

NARRATOR: And the Dutch thought they had just the nutcracker. HETE had a ready-made understudy. It came from Italy.

[On Tape in Italian] Beppo-Sax...

NARRATOR: Beppo-Sax was an Italian satellite carrying Dutch instruments designed to study X-rays. But the satellite also carried instruments that could double as crude gamma ray detectors. It wasn't as fast as HETE, but Beppo-Sax gave the Italian and Dutch scientists the ability to locate bursts relatively quickly.

TITUS GALAMA (Caltech): Beppo-Sax gave us the position within a few hours after the event. That was really critical because typically the afterglow fades away very quickly in optical and so after a few days it was not detectable. You really need to be there within a few hours.

NARRATOR: With HETE lost Dale Frail knew that if he was to stay in the race he had to get his hands on the Beppo-Sax data.

DALE FRAIL: Now, there's always competition in a project such as this when one is aiming for a certain thing. And it's a good competition. It's a healthy competition.

PAUL GROOT: If you know that other people are looking for the same thing at the same time that it drives you a bit harder and you try to get it.

TITUS GALAMA: A healthy drive then.

PAUL GROOT: Yes, absolutely.

NARRATOR: Unwilling to give up, Dale Frail made contact with the Beppo-Sax controllers.

DALE FRAIL: January 1997, I flew to Italy. I showed them our capabilities that we had, the instruments that we had that we'd lined up for the HETE era, and struck a collaboration.

NARRATOR: Not only did Frail have the largest radio facility in the world, but his colleagues had the biggest optical telescope, the Keck. That was crucial, because it was only in visible wavelengths that the distance to an afterglow could be measured precisely.

Unlike gamma rays, visible light can be focused by telescopes and broken into a spectrum of colors. As a beam of light passes through galaxies full of dust and gases, specific wavelengths are absorbed, leaving a characteristic pattern of dark lines in the spectrum. The further away the light source, the more these dark lines move toward the red, because as light travels through an expanding universe it is stretched and shifted towards the longer wavelength of red.

If the explosion that produced the gamma rays left an optical afterglow, Dale Frail's team could use red-shift to measure the distance. But first, the Italian satellite would have to catch one of the unpredictable gamma ray bursts.

Although the Dutch scientists didn't know it, the Italians agreed to give Dale Frail's team their data. Soon after, Beppo-Sax recorded a burst, and Frail's telescopes captured what appeared to be an afterglow.

DALE FRAIL: We found something very interesting, something we hadn't seen before. We thought we may have found an afterglow. It sort of fit the bill.

NARRATOR: The Beppo-Sax satellite had traced the source of the burst to a patch of sky in the constellation of the Snake. When Frail studied the area he discovered a faintly glowing source which he thought was the afterglow. The source was in a distant galaxy. It looked like final proof that the bursts were happening far across the universe.

Working flat out, Frail prepared to reveal his findings in the prestigious scientific journal Nature.

DALE FRAIL: It was mentally exhausting, the whole procedure of writing the paper, keeping everything quiet for that long.

NARRATOR: At the last minute he got bad news.

DALE FRAIL: And it was accepted, waiting to go to press, and the Dutch team announced a new position for the object. And there was no doubt in anyone's mind that we had gotten it wrong. And this was a pretty big blow.

NARRATOR: When the Beppo-Sax team calculated more precise coordinates the area was much smaller than the original. And Frail's glowing source was outside the new more accurate location. Whatever he had found, it wasn't an afterglow.

PAUL GROOT: You write this Nature paper, and then at the very last moment, at the very last moment you have to retract that. You must be really down, really depressed. I can really imagine that.

DALE FRAIL: We expended all this energy trying to study this object and there it was, off outside of the field of view of the gamma ray burster, doing its own little dance, mocking us if you like, for our foolishness.

NARRATOR: When Beppo-Sax caught its next burst, the timing couldn't have been worse for Dale Frail.

DALE FRAIL: This was almost at the lowest point for us. We are completely exhausted from the last event, the false event. We've worn ourselves out. We begin somewhat half-heartedly to go after this next event.

NARRATOR: The Dutch were also after it. But back in Holland things weren't much better. The Italians were refusing to hand over the coordinates they needed.

TITUS GALAMA: And then at some point it turned out that he couldn't give me—this was a political decision made higher up...had to do with the Italian collaborators—that he couldn't give me the position.

NARRATOR: With the afterglow fading, there was a string of frantic phone calls. Dale Frail broke the deadlock.

DALE FRAIL: I felt very strongly that the best way to solve this problem was to indeed make the information public to everyone, and I told the Italians this.

NARRATOR: But the Italians gave the coordinates to the Dutch on strict conditions. They had permission to look for the afterglow at radio wavelengths only, not in the crucial optical wavelengths.

As fate would have it, that very night the Dutch had booked time at an optical observatory called La Palma. Paul Groot had to decide whether to play by the rules.

PAUL GROOT: We were in a dilemma at that point because we had our position and I realized that it was still visible but it would set, the source would set below the horizon quite soon. So then the question was, "What are we going to do? Are we going to go wait till we get a call saying 'yes' or 'no' or are we going to go ahead and go for it?" And at that time we thought, "Well, this is science. We are never going to get this chance again." So that's when we decided to call the telescopes on La Palma and tell them, "go."

TITUS GALAMA: You just try whatever you can. So that's what we did. That's the race.

PAUL GROOT: ...and deal with any consequences later.

NARRATOR: Two images, taken a week apart, revealed a rapidly fading optical source, an afterglow.

TITUS GALAMA: That was just amazing, at the point where...that I remember very well...at the point we were looking at that screen and we saw that there was this star, this little thing there. And, really, I realized immediately this must be it. I felt that...my intuition told me...this must be it. And then I really felt like, this has been 30 years and there it is.

PAUL GROOT: There it is.

NARRATOR: What was good news for the Dutch was a bitter blow for Dale Frail.

DALE FRAIL: It was late at night. I was very tired. I had already been punched once from the previous burst, and this was a second punch, and this was a bad, bad time. So I went home, threw the telegram on the table and told my wife, "It's over. It's all done."

NARRATOR: As more afterglows came in, it became clear that the bursts were coming from vast distances. Dale Frail's luck finally turned when his team got a crucial red-shift that precisely located one blast at a distance of nine billion light years from Earth.

DALE FRAIL: And that distance told us unambiguously that the thing had to be outside of our galaxy—in fact located at a distance when our universe was about half of its present age—and that these things were what we call cosmological, truly cosmological.

STAN WOOSLEY: This, of course, was an hour of triumph for Bohdan Paczynski because he had been championing the cause of extra-galactic gamma ray bursts for many years. But this was such clear confirmation. It was a great victory for him. No, no longer the nut or the voice crying in the wilderness, but the seer of the future.

NARRATOR: The debate was over. A neutron star couldn't create the energy to beam gamma rays from such vast distances. Don Lamb's theory was dead.

DON LAMB: It was kind of like a triple whammy. The launch of HETE failed and we lost HETE, and after battling to get an opportunity to be the team even so to unravel the mystery, Beppo-Sax turned out to be able to do it. And then on top of all that, I turned out to be wrong about the distance to gamma ray bursts and what they are.

STAN WOOSLEY: As we began to get red-shifts for the gamma ray bursts we were startled at how much energy was involved, we were expecting large numbers but not this big. I mean, to put it into perspective, when a rather large nuclear bomb, say ten megatons, goes off, less than one pound of matter is turned into energy in that explosion.

DALE FRAIL: This is the kind of energy you need if you took the mass of our sun, our sun, and turned it into energy into ten seconds, pure energy, E=mc2

NARRATOR: If one mystery was solved an even greater puzzle had taken its place.

STAN WOOSLEY: The entire sun being turned instantly into gamma rays, how on earth could one possibly do that?

DALE FRAIL: This is something that we still have a hard time getting our brains around, but we've come to accept now that it's our brains that are the problem and not the energies involved.

NARRATOR: Astronomers had finally revealed the true enormity of the blasts creating gamma ray bursts. They are the most powerful explosions since the big bang. But what object could release so much energy, defying all notions of what was physically possible?

BOHDAN PACZYNSKI: We do know from history, that now and then a textbook truth, which was valid for...considered to be valid for hundreds of years, is changed. We have either completely new interpretation or we actually find that the old one is fundamentally wrong. It happens.

NARRATOR: For 25 years, scientists had searched for the source of these powerful explosions. They had turned to the sun and found nothing. They had looked to the stars that surround our sun and found nothing. They had scoured the galaxy and beyond.

Now that they had finally found the explosions at the far reaches of the universe they were desperate to understand what objects might be capable of such staggering violence.

The first clue was where the bursts were found.

STAN WOOSLEY: As time was passing, we were finding that the gamma ray bursts really did seem to happen, not just randomly in the galaxies where they occurred, but in regions where star formation was going on.

NARRATOR: In stellar nurseries throughout the universe stars form where there are clouds of gas and dust. The denser clouds give rise to giant stars, ten times more massive than our sun, that end their brief lives with a bang as supernovae. It was now clear that these explosions and the neutron stars they create could not themselves trigger the gamma-rays scientists were detecting.

Stan Woosley asked what might happen if the dying star wasn't ten, but thirty times more massive than our sun, exploding not as a supernova but as something entirely different, a hypernova.

Hidden within this fireball would be an object far more powerful than a neutron star with the most intense gravitational field known to science, a black hole.

STAN WOOSLEY: And then we've created a very interesting object. You have a star that's made a black hole in its middle. And what's the natural inclination is for everything to fall in the hole and you see the star, and suddenly it disappears. It's gone.

NARRATOR: Stan Woosley's colleague Andrew MacFadyen built a model depicting the last few seconds in the life of one of these colossal stars.

ANDREW MacFADYEN (Caltech): This is a star that's dying and the way a star this big dies is that it creates a black hole at its center. So this is the, in a way, the death cry of the star and the birth cry for a black hole.

NARRATOR: But even a star collapsing into a black hole could not create a gamma ray burst. There had to be a twist.

ANDREW MacFADYEN: Well this whole star was spinning when it was born and it's spinning now. So this material that's falling into the black hole, it's like a big electric motor in the center of a star, but incredibly powerful.

NARRATOR: In this cross-section the black hole is a speck at the center of the screen. The red areas are the material spinning around it. The combination of the spin and the intense gravitational field converts huge amounts of matter into pure energy. But the spin does something even more remarkable, it focuses the energy into two powerful jets.

ANDREW MacFADYEN: What the blue stuff is—they're called jets—those blue things are the things that take the energy from near the black hole and transport it way far away from the star and make the huge gamma ray bursts. The gravity is insanely powerful, and much, much stronger than anything we're used to. That's the source of energy for these things.

NARRATOR: If Stan and Andrew's theory is right, then every day in the universe a massive spinning star collapses into a black hole. As the star is consumed by the black hole at its center, focused beams of intense energy shoot into space. These create the bursts of gamma rays seen from Earth. In seconds the colossal star disappears, consumed by one of the most powerful explosions since the big bang.

As astronomers gather more evidence for this model, some wonder what would happen if a hypernova went off near Earth. At the University of Haifa is a man who has thought long and hard about the affects of a direct hit on our planet. Arnon Dar is a professor of astrophysics.

ARNON DAR (The Technion Institute, University of Haifa): The gamma ray bursts are the largest explosions in the universe after the big bang, and the amount of energy released in such an explosion is a billion times a billion times a billion of hydrogen bombs. And this explosion is taking place in a short fraction of a second.

Say that the gamma ray burst occurs in our galaxy, and let's say that it occurs in that direction. Then the first thing that you would see when the flash of gamma rays arrive to our atmosphere you see a big flash of blue light, tremendous effects which are very similar to those which are when you are standing very close to a nuclear explosion. You would become blind in a very short time. Your skin will be completely burned. Your body will be burned and will be exposed to an enormous dosage of radioactive radiation, which will kill you in a very short time.

NARRATOR: And the same thing would be happening simultaneously all around the planet: a tremendous shock wave causes devastation; the sea boils; hurricanes spread deadly radiation around the globe. All but the most sheltered species are destroyed. The ozone layer is blasted away. And, unprotected, the earth turns under a continuous barrage of deadly cosmic rays.

STAN WOOSLEY: If you had it within just a few hundred light years, it would be sort of like Hiroshima going off all over the world all at one time. But in the whole galaxy there is nothing within a thousand light years that we would expect to produce a gamma ray burst anytime in the future. There are massive stars but they don't seem to be the type that would make a gamma ray burst. So I personally don't think they are an astronomical hazard.

NARRATOR: Most scientists consider such a global catastrophe unlikely. But there is no doubt that anything caught in the beam of a nearby gamma ray burst would be destroyed. And with a destructive force this powerful throughout the universe, Arnon Dar sees an answer to one of the profound questions of our time.

ARNON DAR: There are many of stars with planetary systems where life could develop and precede us by billions of years. They are much more advanced civilization...there may be much more advanced civilizations in this universe. So the question "Where are they? Why didn't they visit us? Why didn't they communicate with us?"

NARRATOR: With billions of galaxies, the laws of probability seem to favor the existence of alien civilizations. Yet as far as we know, we are alone. Arnon Dar believes that gamma ray bursts might explain this paradox.

ARNON DAR: This phenomenon of gamma ray bursts is taking place everywhere in any galaxy in the universe and one by one they sterilize life on all the planets in each galaxy. So this is a very effective sterilization process.

NARRATOR: If Dar is right, then the objects that create gamma ray bursts are truly death stars, destroying life on a galactic scale. But other astronomers see these colossal stars as one of the principle creative forces in the universe, forging new elements that are released as they die. And a new race is on to study them in greater detail.

DON LAMB: HETE 2 was successfully launched on October 9th, 2000 and it's now detected and reported its first bursts.

DALE FRAIL: So now, instead of being notified on a time scale of an hour, which was pretty good four years ago, now I can be told on a time scale of minutes to seconds after the burst has gone off. This opens up a whole new realm of physics, a whole new realm of questions. And that's what gets me out of bed at two o'clock in the morning.

NARRATOR: The light from a recently detected burst began its journey over 12 billion years ago. Such events are among the closest scientists have come to seeing back to the dawn of time, the big bang, some 14 billion years ago. After this primeval explosion, there was no light until clouds of hydrogen and helium ignited to form the first stars. They gave rise to new elements, even the iron that flows through our blood.

DON LAMB: Everything that we're made of, carbon, nitrogen, oxygen, silicon, iron, everything the earth is made of, were formed in the furnaces of these massive stars. The bursts in gamma rays, if these ideas are right, would be being produced by exactly those stars. So by observing the bursts we could find out and determine the moment of first light. We could find out when the first stars formed in the universe.

NARRATOR: Glimpsing this first light, scientists may gain new insights into how the universe evolved.

BODHAN PACZYNSKI: There is always a hope, expectation, that perhaps something very fundamentally new is being discovered, not just a twist on something we already know, perhaps some completely new physics. I mean, this would just be great.

NARRATOR: It took 30 years to track down the most powerful events in the universe. But as astronomers learn more about gamma ray bursts they realize that their work has just begun.

Explore one astronomer's detailed analysis of what could happen to our own planet if a gamma ray burst occurred nearby in our own Milky Way galaxy, on PBS.org or America Online, keyword PBS.

To order this show or any other NOVA program for $19.95 plus shipping and handling call WGBH Boston Video at 1-800-255-9424.

Next time on NOVA, a battle over bones fuels an archeological debate. They were compassionate, they were caring, they were human: an evolutionary dead end or our ancestors? Neanderthals on Trial.

NOVA is a production of WGBH Boston.

Major funding for NOVA is provided by the Park Foundation, dedicated to education and quality television.

This program is funded in part by the Northwestern Mutual Foundation. Some people already know Northwestern Mutual can help plan for your children's education. Are you there yet? Northwestern Mutual Financial Network.

Science: it's given us the framework to help make wireless communications clear. Sprint PCS is proud to support NOVA.

And by the Corporation for Public Broadcasting, and by contributions to your PBS station from viewers like you. Thank you.

This PBS.



PRODUCTION CREDITS

Death Star

Produced by
David Sington

Narrated by
Stacy Keach

Directed by
David McNab

Associate Producer
Duncan Copp

Edited by
David Fairhead

Produced for NOVA by
Sarah Holt
Susan K. Lewis

Camera
Kris Denton
Clive North

Sound Recordists
Glenn Bates
Doug Dreger
Steve Shearn

Music
Michael Bacon

Design
Hobbins Sides

Animation
Red Post Production
Andrew Jadavji
Gareth Edwards

Additional Animation:
3D Cosmic Visualizations for NCSA
University of Illinois

Producer and Art Director
Donna Cox

Art Director and Choreographer
Robert Patterson

Visualization Programmer
Stuart Levy

NCSA Animator
Meghan Thornton

Production Manager for Dox Productions
Selina Kay

Production Assistant
Jennifer Callahan

Assistant Editor
Dan Van Roekel

Online Editors
Mike Curd
Fernando Guerreiro

Colorist
Mark Kueper

Audio Mix
Richard Bock
Phil Reed

Archival Material
NASA
Agenzia Spazale Italiana
Goddard Space Flight Center
Robin Scagell
Galaxy Picture Library
PPARC
TRW Space Electronics
Caltech
STScl
KCET
Roger Smith
AURA/NOAO
David Malin Images
Michael Norman

Special Thanks
National Radio Astronomy Observatory
The Anton Pannekoek Institute, Amsterdam
The Bradbury Science Museum
The Technion Institute Haifa
Stephen Thorsett
Tom Cline
Neil Cemels
Chryssa Kouveliotou
Paul Vreewijk
Shri Kulkarni
National Solar Observatory/Sacramento Peak
Princeton University
Charles Dermer
Brenda Dingus
Trevor Weekes

NOVA Series Graphics
National Ministry of Design

NOVA Theme
Mason Daring
Martin Brody
Michael Whalen

Post Production Online Editor
Mark Steele

Closed Captioning
The Caption Center

Production Secretaries
Queene Coyne
Linda Callahan

Publicity
Jonathan Renes
Diane Buxton
Katie Kemple

Senior Researcher
Ethan Herberman

Unit Managers
Sarah Goldman
Jessica Maher
Sharon Winsett

Paralegal
Nancy Marshall

Legal Counsel
Susan Rosen Shishko

Business Manager
Laurie Cahalane

Post Production Assistant
Patrick Carey

Associate Producer, Post Production
Nathan Gunner

Post Production Supervisor
Regina O'Toole

Post Production Editors
David Eells
Rebecca Nieto

Supervising Producer
Lisa D'Angelo

Senior Science Editor
Evan Hadingham

Senior Series Producer
Melanie Wallace

Managing Director
Alan Ritsko

Executive Producer
Paula S. Apsell

A Dox production for NOVA/WGBH and Channel 4.

© 2002 WGBH Educational Foundation

All rights reserved

 

About NOVA | NOVA Homepage | Support NOVA

© | Created September 2006

Support provided by

For new content
visit the redesigned
NOVA site