GRB 090423 at a redshift of z~8.1
  Gamma-ray bursts (GRBSs) are produced by rare types of massive stellar
explosions. Their rapidly fading afterglows are often bright enough at optical
wavelengths, that they are detectable up to cosmological distances. Hirtheto,
the highest known redshift for a GRB was z=6.7, for GRB 080913, and for a
galaxy was z=6.96. Here we report observations of GRB 090423 and the
near-infrared spectroscopic measurement of its redshift z=8.1^{+0.1}_{-0.3}.
This burst happened when the Universe was only ~4% of its current age. Its
properties are similar to those of GRBs observed at low/intermediate redshifts,
suggesting that the mechanisms and progenitors that gave rise to this burst
about 600 million years after the Big Bang are not markedly different from
those producing GRBs ~10 billion years later.
