Astronomers from the Sloan Digital Sky Survey III (SDSS-III) made the largest 3-dimensional map of distant galaxies. The map involved hundreds of scientist that were part of an international team. The map shows a million galaxies and makes possible to measure dark energy, which is the unexplained force that makes the universe expand.
The large-scale structure of the Universe from the SDSS-III and its Baryon Oscillation Spectroscopic Survey (BOSS), shows a decade of collected measurements of 1.2 million galaxies. The map portrays over volume of 650 cubic billion light years and has allowed making “the best” measurements yet of dark energy, says one of the co-leaders of the project, Jeremy Tinker of New York University. The released of the map is available on SDSS-III website.
This map makes possible to measure the expansion rate of the Universe and to calculate the amount of dark matter and dark energy that forms the present-day Universe.
To measure the expansion rate of the Universe, BOSS determines the size of the baryon acoustic oscillations (BAO) in a 3D distribution of galaxies.Bao detects pressure waves that traveled through the Universe when it was 400 thousand years old. Those pressure waves became frozen at that point in the matter distribution of the Universe. The result of these frozen waves is what scientist call the acoustic scale, which is the characteristic separation of galaxies.
It is important to mention that currently, the Universe is 13.8 billion years old, to understand how early pressure waves are. Pressure waves are viewed, according to New Scientist, as if they were sound waves that produce an “acoustic” imprint: the acoustic scale.
According to the map release, Ariel Sanchez of the Max-Planck Institute of Extraterrestrial Physics was the leader of the works that estimated the exact amount of dark matter and dark energy based on the BOSS data. He explained that knowing how the exact proportion of the acoustic scale across cosmic history allows measuring the Universe’s accelerating expansion rate.
Dark matter attracts galaxies and expands the universe
Astrophysicist David Schlegel, who works at Lawrence Berkeley National Laboratory (Berkeley Lab), says that the map can see galaxies being gravitationally pulled towards other galaxies by dark matter. Schlegel, who is also a principal investigator for BOSS, says that their map makes possible to study 95 percent of the Universe that is dark. He added that on much larger scales, they could see the effect of dark energy “ripping the Universe apart.”
The map also reveals the characteristic signature of the coherent movement of galaxies toward regions of the Universe with more matter. Dark matter attracts these areas due to its force of gravity. The release says that the Monthly Notices of the Royal Astronomical Society ahs received this week a collection of papers describing these results.
Source: SDSS