Astrophysicists around the world released the world's largest 3D map of the Universe on Monday, the result of the analysis of more than four million galaxies and quasars, ultraluminous objects emitting colossal energy.
"There was still a lack of data"
"This work simply gives us the most complete history of the expansion of the Universe to date," said one of the researchers involved in the project, Will Percival, of the University of Waterloo. The map, the fruit of a collaboration of more than twenty years between hundreds of scientists from around thirty different institutions around the world, was drawn up from the last cosmological survey of the SDSS (Sloan Digital Sky Survey), called "The extended Baryon Oscillation Spectroscopic Survey" (eBOSS), around a telescope located in New Mexico, in the United States.
Thanks to the numerous theoretical works carried out over time on the Big Bang, as well as to the observation of the cosmic microwave background (a weak light radiation left by the Big Bang), the first moments of the Universe are relatively well known to researchers.
Studies on galaxies and distance measurements had also given a good understanding of the expansion of the Universe that has taken place over the past billion years. "However, there was 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.
Supermassive black hole galaxies
The map produced 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 map relating to the Universe six billion years ago in the past, researchers observed the oldest and most red galaxies. For more distant eras, they concentrated on the youngest galaxies, the blue ones. To go back further, that is to say up to eleven billion years, they used quasars - galaxies whose supermassive black hole, in their center, is made extremely bright by the matter which is there submerged.
The map shows that at some point the expansion of the Universe accelerated and has continued to do so ever since. This acceleration seems to be due to the presence of dark energy, an invisible element which integrates into Einstein's general theory of relativity but whose origin is not yet understood, said the Federal Polytechnic of Lausanne (EPFL), who worked on the project.