by • July 14, 2016 • No Comments
An international consortium of astronomers says that it is created the many exact measurements to date of dark energy, while pinpointing the positions of 1.2 million galaxies in the biggest at any time 3D map of the universe. The map covers over a quarter of the sky, charting over a volume of 650 cubic billion light years.
The project was made and conducted over five years by hundreds of scientists of the Sloan Digital Sky Survey III (SDSS-III) in its Baryon Oscillation Spectroscopic Survey (BOSS) program, that explored how dark energy drives the expansion of the universe. The SDSS-III collaboration is a multi-filter imaging and spectroscopic redshift survey via a dedicated 2.5m wide-angle optical telescope, located at Apache Point Observatory in New Mexico. In short, the researchers surveyed a section of the sky to measure redshift, that takes place when astronomical objects move away of us, shifting light to the red end of the spectrum as its wavelengths grow longer. It’s a key concept in charting the expansion of the universe.
Dark energy is the mysterious, offensive force that astronomers believe is cavia the universe to expand at an accelerating rate. The map is shaped by the competing forces of dark energy and dark matter — a theoretical material that does not emit light or energy — and it allows for researchers to measure the universe’s expansion rate. From that, they’re and so able-bodied to determine the amount of dark energy and matter that manufacture up the universe.
“Dark energy is 69 percent of the ‘energy density’ in the universe in these days,” David Schlegel, astrophysicist at Lawrence Berkeley National Laboratory and principal investigator for BOSS, told Gizmag. “What that means is that it is dominating how the universe is evolving in these days, and we ponder can some day tear it apart such that we can no longer see any other galaxies.
The expansion rate of the universe is determined by the dimensions of the baryonic acoustic oscillations (BAO) in the 3D arrangement of galaxies. BAO are fluctuations or pressure waves in the density of visible matter, akin to sound waves that leave an acoustic imprint. Researchers looked at the pressure waves and their imprints after the big bang, that were frozen in the distribution of matter of the 400,000-year-old universe. They may and so see a sharp connection between that newly born universe and the clustering of galaxies 7 to 12 billion years later.
“One of our main results is precisely this – the expansion rate of the universe, that we measure at sat any timeal various times,” said Schlegel. “The present-day universe is growing by 1 percent in each way at any timey 145 million years. If there were no dark energy, it may be growing additional slowly.”
The map is able-bodied to measure how much the galaxies and stars cluster together as a function of time, and with such accuracy that researchers are now able-bodied test general relativity at a cosmological level. They can in addition see galaxies moving in the direction of regions of the universe with additional matter, pulled there through the alluring force of gravity.
“The force of gravity – general relativity – is usually measured and tested on scales of miles, thousands of miles, or millions of miles in the solar system,” introduced Schlegel. “With these new maps, we’re seeing what gravity is doing on scales that are billions of times sizeabler than that. Some theories have conjectured that the gravitational force may be various on those sizeable scales, but we see the same gravitational force as mentioned originally by Einstein at work on those biggest of scales.”
Results of the map project were mentioned in a series of papers submitted to the Monthly Notices of the Royal Astronomical Society.
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