University scientists observe real-time supernova

Two Princeton researchers, Alicia Soderberg and Edo Berger, have become the first humans in recorded history to witness the explosion of a supernova in real time.

Soderberg, who is a postdoctoral research associate in the astrophysical sciences department, was monitoring x-ray emissions from NASA’s Swift observation satellite on Jan. 9 when a bright light filled her screen. “I knew immediately that this was an extraordinary event, just by its brightness alone, and I sprung into action,” Soderberg explained at a press conference.

What Soderberg had witnessed were the x-ray emissions from an exploding supernova. Humans notice most supernovae about a month after the initial explosion, Soderberg said, explaining that the light takes a few weeks to reach its peak intensity, at which point the supernova can be seen even by amateur astronomers.

By the time scientists notice the light, however, “most of the fireworks are over,” Soderberg said. Because Soderberg caught the x-rays that were emitted at the moment of explosion, she was able to monitor the entire collapse of the star.

A supernova occurs when a star runs out of fuel, Geoff Brumfiel, a science writer for Nature, explained in the journal, which published Soderberg and Berger’s report of the discovery in this week’s issue. “A star lives its life in a balancing act: gravity crushes its gas, while the energy of nuclear fusion pushes it back outward,” he explained. Without the energy from nuclear fusion to push it outward, the star collapses. Sometimes, the quick collapse results in a giant explosion, known as a supernova.

Harvard astronomy professor Robert Kirshner said at the press conference that the x-rays Soderberg observed resulted from the shock of the exploding core of the star hitting the outer shell.

After witnessing the explosion, which took place 100 million light-years away in the constellation Lynx, Soderberg alerted the scientific community and asked Berger, also an astrophysical sciences postdoctoral research associate, to help her monitor the event. Soon, researchers from California to Taiwan were training their telescopes on the Lynx constellation to complete the first observation of a supernova from birth to death.

The initial burst of x-ray radiation lasted less than five minutes, Soderberg said, but scientists were nevertheless able to track the supernova’s evolution.

“A few weeks later, we had accumulated an outstanding sequence of optical spectra of a young supernova,” Jean-Rene Roy, deputy director and head of science at the Gemini Observatory in Hawaii, said in a statement.

Continued observation and data collection will help scientists learn new information about the mechanics of supernova explosions. Soderberg said in an e-mail to The Daily Princetonian that she has “already lined up observations in the visual band and at radio wavelengths that will last throughout the end of 2008 and into 2009.”

In addition, the chance discovery of the x-ray radiation will encourage scientists to focus more attention on monitoring x-rays in the future, which will lead to discoveries of more exploding supernovae, Berger said in a statement from Caltech.

“Seeing the shock breakout in Xrays can give a direct view of the exploding star in the last minutes of its life and also provide a signpost to which astronomers can quickly point their telescopes to watch the explosion unfold,” Berger explained.

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Soderberg said in an e-mail to the ‘Prince’ that for her, the most surprising aspect of the discovery was her incredible luck. “It was statistically impossible that we should be studying that particular part of space at that exact moment when the star exploded. We got extremely lucky,” she said.

But Kirshner, who has mentored Soderberg since she was in college, said that more than luck was working in Soderberg and Berger’s favor. “She was lucky, but if you’re active and you’re energetic, you manufacture your own luck,” he explained.