measurement of the expanding Universe

Astronomers just make the most precise measurement yet of the expanding Universe.    An illustration of how astronomers used quasar light to trace the expansion of the universe. Image © Paul Hooper at Spirit Design, with Mat Pieri and Gongbo Zhao, ICG

Astronomers from the Sloan Digital Sky Survey have used 140,000 distant quasars to measure the expansion rate of the Universe when it was only one-quarter of its present age. This is the best measurement yet of the expansion rate at any epoch in the last 13 billion years.

The Baryon Oscillation Spectroscopic Survey (BOSS), the largest component of the third Sloan Digital Sky Survey (SDSS-III), pioneered the technique of measuring the structure of the young Universe by using quasars to map the distribution of intergalactic hydrogen gas. Today, new BOSS observations of this structure were presented at the April 2014 meeting of the American Physical Society in Savannah, GA.

Measurement of the expanding Universe

Artist’s conception of how the Baryon Oscillation Spectroscopic Survey uses quasars to make measurements. The light these objects sends out gets absorbed by gas in between the receiver and the source. Credit: Zosia Rostomian (Lawrence Berkeley National Laboratory) and Andreu Font-Ribera (BOSS Lyman-alpha team, Berkeley Lab.)

These latest results combine two different methods of using quasars and intergalactic gas to measure the rate of expansion of the Universe. The first analysis, by Andreu Font-Ribera (Lawrence Berkeley National Laboratory) and collaborators, compares the distribution of quasars to the distribution of hydrogen gas to measure distances in the Universe. A second analysis team led by Timothée Delubac (École Polytechnique Fédérale de Lausanne, Switzerland) focused on the patterns in the hydrogen gas itself to measure the distribution of mass in the young Universe. Together the two BOSS analyses establish that 10.8 billion years ago, the Universe was expanding by one percent every 44 million years.

“If we look back to the Universe when galaxies were three times closer together than they are today, we’d see that a pair of galaxies separated by a million light-years would be drifting apart at a speed of 68 kilometers per second as the Universe expands,” says Font-Ribera.

via universetoday

source Sloan Digital Sky Survey