gollum123 writes with a link to the Berkley site about an impressive star explosion that took place some tens of millions of years ago. We first caught sight of it in 2004, when there was a bright outburst, ahead of a massive supernova. "All the observations suggest that the supernova's blast wave took only a few weeks to reach the shell of material ejected two years earlier, which did not have time to drift very far from the star. As the wave smashed into the ejecta, it heated the gas to millions of degrees, hot enough to emit copious X-rays. The Swift satellite saw the supernova continue to brighten in X-rays for 100 days, something that has never been seen before in a supernova. All supernovae previously observed in X-rays have started off bright and then quickly faded to invisibility."