To catch a failing star

For the first time in history, astronomers have caught a supernova—a star blowing itself to bits at the end of its life—at the instant of detonation.

The unprecedented new observations flowing from this discovery are giving astronomers a deeper understanding of just what happens when a star explodes.

Credit: NASA/Swift Science Team/Stefan Immler.

On January 9, Alicia Soderberg, an astronomer at Princeton University, was using NASA’s SWIFT satellite to study x-rays from an earlier supernova in the galaxy NGC 2770, 90 million light years from Earth, in the constellation Lynx.

What she had the amazing luck to witness instead was a brilliant burst of x-rays so intense that they overwhelmed the satellite’s detector.

“I truly won the astronomy lottery,” Soderberg says. “A star exploded right before my eyes,”

She instantly realized that the blast was the long-sought signature of the birth of a supernova. Within minutes she alerted astronomers around the world, allowing them to observe the first hours and days of a supernova for the first time.

Until now, scientists could only study supernovas when visible light from dust and gas around the star reached Earth. But since that light arrives days or weeks after the actual explosion, the scientists were left in the dark concerning supernovas’ first days.

Astrophysicists have a working theoretical understanding of how a star dies and creates a supernova. When a massive star runs out of its nuclear fuel, its core collapses under the pull of gravity. The infalling material can reach a speed of a quarter of the speed of light, and a temperature of 100 billion degrees. When the core has collapsed as much as it can, into what’s known as a neutron star, it rebounds, creating an incredibly powerful shock wave. When that shock wave hits the dying star’s surface, it generates an intense blast of ultraviolet light or x-rays.

It was those long-predicted x-rays that Soderberg detected, for the first time.

Now scientists can start to check their theories against real data.

Supernova 2008 D, as Soderberg's discovery is now known, is already the most studied supernova in history. Her incredibly good luck has become astronomy’s great gain. It will let astronomers and astrophysicists fill in the gaps in their understanding of the sudden death of massive stars and the fiery birth of neutron stars and black holes.

Robert Adler