Figure 1: The Universe as we know it.
A 360° vista showing the entire sky, with visible structures stretching back in distance, time and redshift. (The immediate light and dust from our own Galaxy, the Milky Way, obscures all light from outside sources in its plane.) The most distant light we observe comes from the radiation left over from the Big Bang: the cosmic microwave background. As we descend the chart, we find the most distant objects known, followed by a web of Sloan Digital Sky Survey (SDSS) quasars and galaxies. Closer to home, we start to see a collection of familiar ‘near’ galaxies (triangles). At z=0.7554 (in the favoured cosmological models), the Universe undergoes a transition from a slowing expansion to an accelerating one. Objects with z<0.7554 are observed at an epoch when the Universe's expansion is accelerating, whereas objects farther away are observed at an epoch when the Universe's expansion is decelerating. Also marked are all Swift GRBs with known distances (blue stars); SN 1997ff, the most distant type Ia supernova at z=1.7; and the archetypal large galaxy cluster, the Coma cluster. The most distant GRB, reported in this issue1,2,3, is at redshift z=6.295, comparable to the most distant galaxies found by the Subaru Deep Field (SDF) survey, and the most distant SDSS quasar. (Courtesy of J. R. Gott and M. Juric10.)
