The aging star, in a previously unknown galaxy, exploded in a7.5 billion light years away, its light finally reaching Earth early Wednesday.
Thewere detected by ‘s Swift satellite at 2:12 a.m. “We’d never seen one before so bright and at such a distance,” NASA’s Neil Gehrels said. It was bright enough to be seen with the naked eye.
Bad Astronomy has a pretty good writeup on the matter, with more information on the satellite used, including the following information:
Swift is a satellite in low Earth orbit, and it sees a large portion of the sky at once. When gamma rays from a GRB are detected by Swift, it immediately (in a few seconds!) sends down the rough coordinates of the burst so other telescopes can observe it as quickly as possible — many GRBs fade to invisibility in seconds. So a telescope looking at the same part of the sky as Swift cuts down even those precious seconds, getting the burst simultaneously in optical light as Swift sees the gamma-rays.