From Science:
In a stroke of unprecedented good luck, an international team of astronomers has caught a stellar explosion called supernova at the very beginning of the blast. Although the spectacular deaths of massive stars have been well-studied, astronomers have never been able to observe one any sooner than a few days after its beginning.
The supernova called 2008D neatly and surprisingly solved such problems for its discoverers, led by astrophysicist Alicia Soderberg of Princeton University. On 9 January, she and her colleagues were using the x-ray telescope aboard NASA’s Swift spacecraft to observe a month-old supernova called 2007uy, located in a galaxy called NGC 2770, nearly 90 million light-years away. Suddenly, a blinding light appeared elsewhere in the galaxy, and Soderberg and her colleagues immediately recognized it was the beginning of an entirely new supernova. They contacted colleagues across the United States and seven other countries, who quickly trained eight more telescopes and arrays on the event. In Nature tomorrow, the 43-member team reports that the characteristics of the x-ray burst they detected and then studied for 30 days conforms exactly–in terms of the brightness of the radiation, its precise rate of dimming, and the speed with which debris traveled through the galaxy–to what astronomers had been assuming for decades about the shock wave of a supernova blowing apart the outer layers of a star. They detected no gamma rays associated with the blast, confirming another prediction of the models.
More here.