Astronomers Capture Star Exploding

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Astronomers have witnessed for the first time a star at the very moment it exploded as a supernova. This supernova, in a nearby galaxy, produced a burst of X-rays that lasted 10 minutes and signaled the death of the star. Soon, telescopes around the world focused in on this event to capture X-rays, radio waves and visible light from the dying star.

MICHELE NORRIS, host:

For the first time ever, astronomers have witnessed a star at the very moment it exploded. Our story involves two young astronomers, a NASA satellite and a bit of really good luck.

NPR's Richard Harris tells this tale of a supernova.

RICHARD HARRIS: Ever since she graduated high school, Alicia Soderberg has been fascinated by giant stars that go bang - supernovas. Among other things, these explosions have created the carbon and other vital atoms in our bodies. On January 9th, she was using NASA's Swift satellite to study a supernova that had appeared in December in another galaxy.

Dr. ALICIA SODERBERG (Hubble Postdoctoral, Carnegie-Princeton fellow, Princeton University): This is a really exciting field, so I love to see the data as soon as they come off the telescope or the satellite. And right away, I realized that there was an extremely bright new source in that galaxy that wasn't there the last time I looked at it.

HARRIS: Something very violent had happened and whatever it was produced a powerful blast of X-rays.

Dr. SODERBERG: I didn't immediately think it was a supernova because we know that a supernova only happens every 100 years per galaxy. So, to make two supernovae in a matter of about a month is pretty much unheard of. But I knew it had to be exciting just because it was so bright.

HARRIS: Soderberg had just arrived at Princeton University after earning her PhD. But she knew all the right people in the world of high energy astrophysics, the kind of people who would be really interested in finding out about this object.

Dr. SODERBERG: So, there was a bit of running around and frantic phone calls, et cetera, and at that time I did alert the community that something really exciting had happened so other groups could also begin to study this object.

HARRIS: Soderberg and her collaborators quickly got the Gemini North telescope in Hawaii to look at the source of the X-ray burst. And in the meantime, dozens of other astronomers read her bulletin and got their telescopes pointed toward the same galaxy. One of those astronomers was another freshly minted PhD. Maryam Modjaz is a Miller Institute postdoc at U.C. Berkeley.

Dr. MARYAM MODJAZ (Postdoctoral, University of California, Berkeley): My colleague, Professor Joshua Bloom and I, triggered the Gemini South telescopes in Chile to see if you see the signature of a supernova.

HARRIS: So, here are two young astronomers observing the same event using twin telescopes, Gemini North and South. They both conclude it's a supernova and not only that, Modjaz and her colleagues at Berkeley happened to have been looking at the same galaxy that Soderberg was also studying.

Dr. MODJAZ: So we have data before the supernova, the new one went off. Only three hours before it went off and again later 17 hours after it had gone off, in X-rays.

HARRIS: From those observations, Modjaz was able to figure out what the star looked like before it exploded. She infers that the explosion wasn't completely spherical but maybe more doughnut-shaped. Naturally, Alicia Soderberg, who discovered the supernova, also gathered a huge amount of information about it, with the help of 42 collaborators. Their findings are being published in Nature magazine. And her observations help tell the story of how a star dies when it becomes a supernova. It starts when a star much more massive than our own sun collapses under its own gravitational weight. That generates a giant shockwave.

Ms. SODERBERG: The shockwave races out through the star and actually explodes it. What's interesting is that a lot of energy sort of gets bottled up within that star and it's trapped behind the shockwave. So, once the shockwave reaches the edge of the star, it's sort of like opening the floodgate and all of this energy comes out.

HARRIS: That's the burst of X-rays that Soderberg witnessed for the first time. This is an important first in astronomy, but Soderberg says soon these observations will be commonplace. That's because a new generation of satellites will soon be able to search for X-rays from thousands of galaxies all at once.

Ms. SODERBERG: These new satellites are going to be detecting supernovae every day.

HARRIS: So, you are about to be scooped big time but you got lucky.

Ms. SODERBERG: Yes. That's another way of putting it. I didn't think of that. Yes, I definitely got lucky. This was a very lucky observation, a very lucky discovery.

HARRIS: Richard Harris, NPR News.

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