An extensive cosmological study has led to the creation of the largest 3D map of the Universe ever made. This is the result of the analysis of several million galaxies and other quasars. This work thus traces a more continuous history of the Universe and offers a better understanding of the mechanisms of its expansion.
Astrophysicists from around the world are behind the largest 3D map of the universe ! This project is based on an initiative of the École Polytechnique Fédérale de Lausanne (Switzerland), as explained in a press release of July 20, 2020. This map results from the analysis of four million galaxies and other quasars , these sources of quasi-stellar astronomical radiation.
Hundreds of researchers from some 30 institutions took part in a vast program of cosmological surveys , the Sloan Digital Sky Survey (SDSS). However, this one will have lasted more than twenty years! The map itself was drawn from the last cosmological survey program, namely The extended Baryon Oscillation Spectroscopic Survey (eBOSS). The survey in question was carried out through a telescope located in New Mexico (United States).
Recall that the first moments of the Universe are fairly well known to science. This is the result of many theoretical works on the Big Bang and the observation of the cosmic microwave background. Moreover, the expansion of the Universe is also fairly well understood through studies of galaxies and distance measurements.
However, there was still a lack of data. However, the mission of the eBOSS project has been to fill this gap since its creation in 2012. The objective was to obtain the most complete 3D cartography of the Universe by using new tracers for the first time. The latter are embodied by the galaxies actively forming stars as well as quasars.
The map shows filaments of matter as well as voids defining the structure of the Universe , when it was about 380,000 years old. As for the Universe 6 billion years ago, researchers are talking about the oldest (and reddest) galaxies. In the case of older epochs, we are talking about the youngest (blue) galaxies. As for quasars, these have made it possible to go back up to 11 billion years!
Let's talk about the expansion of the Universe. The map shows an acceleration of this expansion at some point, still present today. According to the researchers, this phenomenon would find its reason in the presence of dark energy . It is an invisible element that integrates with Einstein's theory of general relativity. However, its origin is not yet understood.
The fact that the Universe is expanding has been known for a long time, but the exact speed of this expansion (Hubble constant) remains unknown. Comparing the results of the eBOSS project with previous research, the scientists found a discrepancy. Indeed, this acceleration would be 10% slower compared to the value estimated in the past!