Global team of astrophysicists release largest ever 3D map of the universe


An international collaboration of more than a hundred astrophysicists has published a map that details more than two million galaxies and quasars and eleven billion years of our universe.The team used the 2.5-meter-wide optical telescope from the Sloan Digital Sky Survey (SDSS) in New Mexico to conduct 20-year surveys. More specifically, the map comes from the Baryon Oscillation Spectroscopic Survey (eBOSS), which is designed to measure the expansion of the universe. Yesterday, 23 articles representing more than 500 pages of new research were published.

The map documents the universe when it was only 300,000 years old, revealing filaments, essentially walls of galaxies between the voids of the universe. Using this map, scientists are able to measure the distribution patterns of galaxies.

To get a 3D map, you need three dimensions. The hardest part, says Will Percival, director of the Waterloo Center for Astrophysics at the University of Waterloo and the team’s principal investigator, is figuring out how far away these galaxies are from us.

“The difficulty lies in obtaining this third dimension, this distance from the galaxy. we do that by measuring the galaxy’s redshift, which is how fast the galaxy is moving away from us, ”says Percival. “And we’re using the Hubble expansion of the universe to translate on that speed up to a distance. ”

Hubble’s Law, named after Edwin Hubble, is the speed we use to determine how fast galaxies are moving away from Earth.

Scientists have long known that the universe is constantly expanding in the wake of the Big Bang, but the team behind this map found that it was growing faster than we previously thought, and there is no yet a concrete explanation to explain why.

According to the story revealed on the eBOSS map, the expansion of the universe began to accelerate six billion years ago and has continued to accelerate since.

« TIt’s just really weird because if you just have a standard theory that gravity acts on matter, gravity is an attractive force, it brings things together and it would generally tend to slow the universe down, ”Percival explains. . “Which means there’s physics out there that we don’t know about. “

While there are theories, “none of them are really convincing.” According to Percival, the simplest mathematical explanation would be to take Einstein’s cosmological constant equation and change a sign in it to change the universe from static to make it speed up. Mathematically, it’s a simple thing to do, but when it comes to physics, it’s a lot harder to explain.

In particular, the measure by the eBOSS team of the current rate of expansion of the universe, the previously mentioned Hubble Law, is about 10% lower than the value found from distances to nearby galaxies. It is thought that the mysterious invisible component of the universe that we call “dark energy” has something to do with it, but like many other phenomena in the universe, it remains unexplained.

While this is the largest map to date, Percival is hopeful that the next generation of investigations will bring together more galaxies and potentially solve this mystery by “really mastering the theory of dark energy.”

Some of these projects may include the Dark Energy Spectroscopic Instrument (DESI) and EUCLID, a European Space Agency satellite mission and another study of galaxies. Percival is involved in both. He says DESI is about twenty times faster than the Sloan Telescope they used for this map and it may be a few months away from starting depending on the ongoing pandemic.

“I must emphasize that this is a group collaboration, hundreds around the world on all continents. It has been an incredible team resource and I am very happy to see it come to fruition, ”said Percival.


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