ASTROPHYSICS: A Bright Window into the Very Distant Past

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Science  10 Feb 2006:
Vol. 311, Issue 5762, pp. 745b
DOI: 10.1126/science.311.5762.745b

Gamma-ray bursts are extremely energetic flashes that are related to the deaths of stars. Their afterglows have been traced as x-rays and in the optical spectrum, which puts constraints on the physical mechanisms responsible for the energetic emission. Their brightness means that they are visible at great distances and hence carry information from long ago.

Using the Swift x-ray telescope, Watson et al. have detected the afterglow from the most distant gamma-ray burst yet: GRB 050904, with a redshift of 6.295. Its x-ray emission is highly variable, brightening and dimming on a time scale ranging from a few minutes to half a day. At its height, GRB 050904 was a luminous x-ray source, outshining the brightest quasars at that redshift by a factor of 100,000. Evidence of absorption in its spectrum suggests that oxygen and other elements formed in stars were already widespread in the young universe. This observation indicates that bright and distant gamma-ray bursts, rather than quasars, may be the best background sources for absorption studies of the intergalactic medium within a billion years of the Big Bang. — JB

Astrophys. J. 637, L69 (2006).

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