A violent burst of gamma rays detected on 31 January has been pinpointed to a galaxy at a
redshift of 4.5, making it the most remote such burst ever observed. Its brightness was
enormous – 10 000 times that of the emission from all the stars in the host galaxy.
The
mechanisms fuelling gamma-ray bursts (GRBs) are still unknown. They are by far the most
powerful events known to occur since the Big Bang itself. Candidates include explosions
called hypernovae, or the mergers of two black holes.
The optical counterpart to the
January GRB was identified using the Antu telescope at the European Southern
Observatories site in Chile and its distance deduced from spectroscopic observations.
Attention is now focusing on the properties of the host galaxy.
Meanwhile, a new
telescope has entered the picture. The Hete-2 satellite, launched by NASA last October is
expected to detect hundreds of GRBs a year during its four year lifetime. The experiment is a
collaboration between the US, France and Japan.
