Gamma Ray

Gamma ray bursts are formed by beamed radiation resulting from the explosion of massive stars in the distant universe. The bursts can be seen at many wavelengths, from the optical to the very high energy gamma rays that are used to detect them. Because they are so bright they can be seen to great distances, providing us with a new way to find the highest redshift galaxies.

In 2004 Nasa launched a new satellite called SWIFT specifically designed to study these objects. One of the most exciting aspects of the SWIFT mission is that we may, at last, be able to find extremely high redshift galaxies beyond the current upper limits of redshifts near 7 ( Hu et al. 2002, Kodaira et al. 2003) and that we may be able to map the star formation history at these redshifts in a new way.

On Sept 04 SWIFT found a new GRB called GRB050904, which the ground based observations described here showed to be at a redshift of 6.29. The current observed distribution of GRBs peaks around a redshift of 1, with the most distant known GRB at z=4.5, so that this represents an enormous breakthrough to the high redshifts and encourages us that Swift should be able to detect them at still higher redshifts, beyond the most distant known galaxies and quasars, and possibly even beyond, far into the "dark ages" of the universe when the first galaxies and stars were just begining to form.