Current Issue

July16, 2008

Vol. 108, No. 16

Notebook

Princeton researchers catch a star in the act of exploding

By Brett Tomlinson
Published in the July16, 2008, issue


A digital representation of the explosion of a supernova.
Office of Communications
A digital representation of the explosion of a supernova.
Researcher Alicia Soderberg says she “won the astronomers’ lottery.”
Office of Communications
Researcher Alicia Soderberg says she “won the astronomers’ lottery.”

On Jan. 9, 2008, Alicia Soderberg, a postdoctoral research associate in astrophysics at Princeton, was studying the X-ray emissions conveyed from space by NASA’s Swift satellite when she recognized an extremely bright light on the screen of her computer, saturating the satellite’s view “as if we had pointed a digital camera directly at the sun,” she said. That light, Soderberg and colleague Edo Berger later confirmed, was a supernova — an explosion of a massive star.

Their finding, named Supernova 2008D, or SN 2008D for short, was described in a paper published in Nature May 22. In a May 21 teleconference, Soderberg described the experience as being in the right place, at the right time, with the right telescope. “I truly won the astronomers’ lottery,” she said.

Seeing a supernova is not unusual — the stars are brighter than 100 billion suns. But in the vastness of space, there generally is a delay of days or weeks between a supernova’s explosion and its discovery by astronomers. By then, “most of the fireworks are already over,” Soderberg said.

Soderberg saw the explosion live, or live on tape in a sense, downloading the data from the Swift satellite’s observations while she was at an academic conference in Michigan. She had been using Swift to study another supernova, SN 2007uy, in the spiral galaxy NGC 2770, located 90 million light-years from Earth in the constellation Lynx. Seeing two supernovae in the same galaxy in a matter of weeks is extraordinarily unusual — a one-in-10,000 chance, she estimated. A typical galaxy produces one supernova every 100 years.

The Swift satellite, NASA principal investigator Neil Gehrels explained, was designed to detect and study gamma-ray bursts — brief, intense flashes of radiation — but it also is equipped to observe other “targets of opportunity” in the sky. When the Princeton pair spread the word about the unusual discovery, colleagues turned the lenses of other telescopes, including the Hubble Space Telescope, toward the new supernova, beginning a broad and intensive series of observations. Forty-two authors contributed to the Nature paper that described the birth of SN 2008D.

The use of an X-ray flash, rather than optical observation, to detect a supernova marks a “paradigm shift” and could lead to more discoveries, according to Robert Kirshner, a professor of astronomy at Harvard University and one of Soderberg’s mentors. Soderberg and her co-authors estimate that future wide-field X-ray surveys could detect hundreds of exploding supernovae each year.

Soderberg, who earned her Ph.D. from Caltech and recently completed the first of her five years as a Hubble Fellow and Carnegie-Princeton Fellow, had the good fortune to be the first to observe SN 2008D, but according to Kirshner, luck was only partly responsible for the discovery. “If you’re active and you’re energetic, it helps a lot because you manufacture your own luck, in a way,” he said. “There’s nobody who’s more focused and energetic than Alicia Soderberg.”

See a digital video re-creation of the supernova explosion:

The animation shows an artist's rendering of the shock wave discovered by Princeton University's Alicia Soderberg and a team of scientists. A supernova is born when the core of a massive star (the blue orb) runs out of nuclear fuel and collapses under its own gravity to form an ultradense object known as a neutron star. The shock wave erupts and ripples through the star, emitting X-rays (seen here as bright white light). The remnants of the explosion cool (the white light gets smaller), and then the visual light from the supernova glows (seen as yellow clouds). The fading white dot in the middle of the animation represents a newly born neutron star. Courtesy NASA/Swift/Skyworks Digital/Dana Berry

Click here for the animation.

Post Comments
Tell us what you think about
Princeton researchers catch a star in the act of exploding
Enter the word as it appears in the picture below
Send
By submitting a comment, you agree to PAW's comment posting policy.
CURRENT ISSUE: July16, 2008
July16, 2008: NOTEBOOK
Web Bonus Links