Scientists Study Final Moments of Dying Star

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• JEFFREY BROWN:

  One researcher called it "winning the astronomy lottery." Back in January, astronomers were looking at the remnants of one star when they detected the death of another and the beginning of a supernova as it was happening.

  As seen in this animation, the supernova was created when the core of a massive star collapsed — shown here in blue — and then sent out shockwaves leading to an explosion of X-rays and light.

  After it cooled, its remnants formed what's called a neutron star.

  To help us understand more, we turn to one of the researchers involved with the project, Robert Kirshner, a professor of astronomy at Harvard University.

  So, first, why is it so exciting to actually see this as it's happening?

• ROBERT KIRSHNER, Harvard University:

  Well, ordinarily, when we find supernovae, the event has already taken place, because we find them usually by the optical light, the visible light, the ordinary light that our eye is sensitive to.

  But what's unique about this particular supernova is that it was found by the X-rays that it emits. And it turns out the X-rays come first. They're the signal of the actual energy from inside the star hitting the surface. And this is the first time that a supernova has been discovered from its X-ray emission.

• JEFFREY BROWN:

  All right, tell us a bit more about what you're actually seeing, which is to say, tell us, what is a supernova? What's happening?

• ROBERT KIRSHNER:

  A supernova is the death of a star. And in this case, it's the death of a massive star, maybe 10 or 20 times as massive as our own sun.

  Ordinary stars, like the sun, get their energy by nuclear fusion. They change the hydrogen that they're made of into helium. More massive stars do that, too, but they keep on going and they burn fuels all the way up to iron.

  It turns out that there's something special about iron, and it's the element out of which you cannot get any more energy by nuclear fusion. So what happens in a star, when it's made iron in its core, is that it's poised for disaster.

  And this star collapsed on its inside, fell in under the force of gravity with a tremendous release of energy, equivalent more or less to the whole energy output of the sun for its 10-billion-year life, all of that energy coming out in a few seconds.

  And a blast wave, a powerful shockwave went out through the star. And when that shock hit the surface of the star, it made the surface very, very hot, so it would emit these X-rays, these very short photons, these very high-energy photons that don't come through the Earth's atmosphere.

  So you needed a satellite in order to see this first moment when the shockwave slaps the last little bit of gas in the star.

  And there was one. There is this satellite that NASA has built called Swift. And it was being used by Alicia Soderberg to study another object in that galaxy. And by the best of good luck, she saw this burst of X-rays, this enemy coming out from the birth of a supernova.