View Full Version : Gamma ray bursts

2009-Feb-20, 02:07 AM
I just read a press release about a newly dicovered GRB (GRB 080916C) observed by the Fermi Gamma Ray space telescope, and it said that this burst was about as powerful as 9000 supernovas and was located 12.2 billion lightyears away.

But if it's that far away, shouldn't it be red-shifted an awful lot? And yet it's still gamma rays (which means the original frequency of the radiation must have be ridiculously high, surely)?

Shouldn't it be shifted down more toward the visible spectrum (or beyond?) Or is the redshifting really not that much?

2009-Feb-20, 02:27 AM
The furthest known objects have a z of about 7, which means that a light wave will have 8 times longer wavelength here than at its point of origin. Not nearly enough to shift them from gamma rays to visible, which would be ~5 or more magnitudes, according to wikipedia.

2009-Feb-20, 02:30 AM
Ah right, that makes sense then. Thanks :)