Swift Sees a Star Explode

NASA's Swift mission has caught an exploding in the act of exploding. On 9 Jan 2008 Swift was taking routine observations of the supernova SN2007uy in the galaxy NGC 2770 when something unexpected happened. A second supernova erupted as Swift was watching. The supernova SN2008D (the "D" indicates that this is the fourth supernova to be discovered in 2008) observed in real time. The graph below shows the Swift observations of the X rays from SN2008D. Notice that they start at near zero at time zero. This is when the star exploded. The X-ray intensity rises rapidly until about 60 seconds after the explosion, and then slowly fades away.

Swift has seen stars explode before. Most gamma-ray bursts are believed to be the initial stages of supernovae, and Swift detects about 100 of them a year. SN2008D, however, was unique. At 90 million light years away it is located very close to us, as cosmic distances go, so we have been able to get detailed observations that are not possible with the more distant gamma-ray bursts. Another critical difference is that only a small fraction of supernovae product gamma-ray bursts. Estimates are that only about one in one thousand supernovae produce gamma-ray bursts, so those supernovae are very unusual. SN2008D, however, was a normal Type Ibc supernova. This is the first time that we have witnessed the birth of a normal supernova.

NASA's press release on SN2008D describes the event in detail.