Map of 1.2 million galaxies to reveal universe's expansion

Washington:The largest-ever, three-dimensional map of 1.2 million distant galaxies has revealed one of the most precise measurements yet of the dark energy, currently driving the accelerated expansion of the universe, say a team of scientists. “We have spent five years collecting measurements of 1.2 million galaxies over one quarter of the sky to map out the structure of the Universe over a volume of 650 cubic billion light years," said Jeremy Tinker from New York University, a co-leader of the scientific team carrying out this effort. “This map has allowed us to make the best measurements yet of the effects of dark energy in the expansion of the Universe. We are making our results and map available to the world,” Tinker added. The new measurements were carried out by the Baryon Oscillation Spectroscopic Survey (BOSS) programme of the Sloan Digital Sky Survey-III. The map allows scientists to measure the expansion rate of the universe and, thus determine the amount of matter and dark energy that make up the present-day universe. The universe is presently 13.8 billion years old. “We've made the largest map for studying the 95 percent of the universe that is dark," noted David Schlegel, astrophysicist at Lawrence Berkeley National Laboratory (Berkeley Lab) and principal investigator for BOSS. “In this map, we can see galaxies being gravitationally pulled towards other galaxies by dark matter. And on much larger scales, we see the effect of dark energy ripping the universe apart,” he noted in a paper submitted to the journal Monthly Notices of the Royal Astronomical Society. “We can now measure how much the galaxies and stars cluster together as a function of time to such an accuracy we can test General Relativity at cosmological scales,” added Shirley Ho, astrophysicist at Berkeley Lab and Carnegie Mellon University (CMU). The map also reveals the distinctive signature of the coherent movement of galaxies toward regions of the universe with more matter due to the attractive force of gravity.