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More precise measuring

A yardstick for the universe

In this artistic rendering, each circle, with a radius of 500 million light-years, represents a region that has a greater concentration of galaxies

Zosia Rostomian/LBNL In this artistic rendering, each circle, with a radius of 500 million light-years, represents a region that has a greater concentration of galaxiesZosia Rostomian/LBNL

Astronomers have determined distances between clusters of galaxies with record precision, better establishing the properties of dark energy—a poorly understood form of energy—in empty space, which is accelerating the universe’s expansion since its birth in the Big Bang.  In its first 300,000 years, the universe was filled with a hot, dense gas, made of atomic nuclei, free electrons and radiation.  The expansion of the universe caused this gas to cool and become rarefied, forming stars and galaxies.  However, the waves that propagated in the primordial gas left vestiges in the distribution of galaxies in the Cosmos.  Galaxies tend to accumulate in regions that were once the crests of these waves called baryon acoustic oscillations.  The regular spacing of these crests creates a natural cosmic yardstick, and the increase in the distance between the crests can be used to detect the influence of dark energy.  In today’s universe, this spacing is about 500 million light-years.  During a meeting of the American Astronomical Association, on January 8, 2014, researchers from the Baryon Oscillation Spectroscopic Survey (Boss) reported measurements of baryon acoustic oscillations with a precision of 1%.  The study analyzed more than 1 million galaxies, spread over a region 6 billion light-years across.  Boss is one of the four astronomical survey projects being undertaken as part of Sloan Digital Sky Survey 3 (SDSS-III), in which Brazilian groups are involved.  The project uses a unique telescope, located in New Mexico, United States, which analyzes the light from thousands of galaxies simultaneously.

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