“This work provides us with just the history of the expansion of the Universe the most complete to date”, noted one of the researchers.
astrophysicists around the world have published this Monday, the largest 3D map of the Universe ever carried out, resulting from the analysis of more than four million galaxies and quasars, objects ultralumineux emitting a colossal energy.
“This work provides us with just the history of the expansion of the Universe the most complete to date”, noted one of the researchers, Will Percival, of the University of Waterloo.
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The map, a collaboration of more than twenty years of hundreds of scientists from thirty different institutions in the world, has been compiled from the latest survey cosmology from the SDSS (Sloan Digital Sky Survey), named “The extended Baryon Oscillation Spectroscopic Survey (eBOSS), around a telescope located in New Mexico, in the United States.
Thanks to the many theoretical works carried out over time on the Big Bang, as well as the observation of the cosmic microwave background (a faint light radiation left over from the Big Bang), the first moments of the Universe are relatively well known to researchers.
The studies carried out on the galaxies and the distance measurements had also given a good understanding of the expansion of the Universe that occurred in the course of the past billion years. “There remained, however, a lack of data between the beginning of the Universe, and the current period,” said Kyle Dawson, of the University of Utah and one of the leaders of the project.
Expansion
“In 2012, I launched the project eBOSS with the idea of producing a 3D mapping of the Universe the most complete, using for the first time of new tracers that are galaxies forming active stars and quasars,” said Jean-Paul Kneib, astrophysicist at Ecole polytechnique fédérale de Lausanne (EPFL).
The map shows filaments of matter and voids defining the structure of the Universe from its beginnings, when it was only 380 000 years old. For the part of the card relative to the Universe six billion years in the past, researchers observed that galaxies in the most ancient and the most red. For times more distant, they focused on galaxies young, blue.
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To present herself to the farther, that is to say, until eleven billion years ago, they have used quasars – galaxies in which the supermassive black hole in their centre, is made extremely luminous by the matter that is swallowed.
The map shows that at some point the expansion of the Universe has accelerated and has since continued to do so. This acceleration appears to be due, according to the researchers, the presence of dark energy, invisible, that integrates with the general theory of relativity of Einstein but whose origin is not yet understood. Astrophysicists have known for several years that the universe expands but they are trying since to measure the exact speed of this expansion.
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By comparing the observations made by the program eBOSS to the studies conducted until now on the first moments of the Universe, the researchers found a mismatch between the speeds. The commonly accepted currently, called the “Hubble constant”, is revealed to be 10% slower than the calculated value, detailed EPFL, noting that there is, to this day, no explanation.
