Local or Cosmological?

The Distance to Gamma Ray Bursts

More recent observations make it highly likely that gamma ray bursts are not coming from our galaxy, but are at very large distances. This makes them extremely interesting, because for them to be seen at very large distances they must correspond to events in which as much as 100 times the energy of a supernova is being liberated in a short period in the form of gamma rays. Furthermore, the mechanism producing the gamma rays must be such as to allow the gamma rays to escape without too much interaction with surrounding matter, because that interaction would convert the gamma rays to light of longer wavelength.