Early results from the third Sloan Digital Sky Survey (SDSS-III) have yielded the largest ever three-dimensional map of the distant Universe, based on 14,000 quasars sampled by the Baryon Oscillation Spectroscopic Survey, or BOSS (Anže Slosar et al., preprint at http://arxiv.org/abs/1104.5244; 2011).
Previous large-scale maps were generated by surveying galaxies (at the centre of the map shown here), whereas BOSS uses the light from quasars (outer blue dots) up to eleven billion light years away. These contain supermassive black holes and lie at the centres of very old galaxies. Quasars are the most energetic objects in the Universe, and their light is useful for the study of the structure and evolution of expanding clouds of hydrogen gas.
Acoustic waves created during the early history of the Universe have resulted in an anisotropic distribution of baryonic matter, which oscillates on the scale of 500 million light years. Clumping of matter led to the formation of galaxies, hence precise measurements of the modulations and expansion of the intergalactic gas over cosmological distances will help constrain candidate theories for dark energy.
The 2.5-metre Sloan Telescope is situated in New Mexico, USA, and is used for four separate surveys in SDSS-III, including BOSS, which by 2014 will have scanned 160,000 quasars.
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Chiao, M. Check with the BOSS. Nature Phys 7, 453 (2011). https://doi.org/10.1038/nphys2018