Astronomers at the Sloan Digital Sky Survey (SDSS) used 140,000 distant quasars to measure the rate of expansion of the Universe when it was only a quarter of its present age. This is the best measure of the rate of expansion at any time in the 13 billion years since the Big Bang. Researchers from Irfu (CEA) and CNRS played a major role in this discovery.
The Baryon Oscillation Spectroscopic Survey (BOSS), the main component of the third generation of SDSS surveys, was the first to use gigantic quasar transmitters to map the distribution of intergalactic hydrogen gas and thus measure the structure of the young Universe. The selection of the objects to be observed is carried out by researchers from the Research Institute on the Fundamental Laws of the Universe (CEA) and the final BOSS quasar catalog is produced by researchers from the Astroparticle and Cosmology Laboratory (CNRS/CEA/University Paris Diderot/Observatoire de Paris/CNES) and the Paris Astrophysics Institute (CNRS/Université Pierre et Marie Curie).
Three years ago, BOSS used 14,000 quasars to produce the largest 3D maps of the Universe.
Two years ago, with 48,000 quasars, it detected baryonic acoustic oscillations in these maps, which are evidence of the inhomogeneities of the primordial universe. Today, with more than 140,000 quasars, he has obtained extremely precise measurements of the size of these structures, which were presented at the April 2014 meeting of the American Physical Society in Savannah, Georgia.