Global team of astrophysicists release largest ever 3D map of the universe - Woodstock Sentinel Review

The map has both answered and raised questions about our mysterious universe.

Color indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side. There are 48,741 galaxies in this picture, only about 3 per cent of the total surveyed. Daniel Eisenstein and SDSS-III

An international collaboration of over a hundred astrophysicists has released a map that details over two million galaxies and quasars and eleven billion years of our universe.

The team used the Sloan Digital Sky Survey’s (SDSS) 2.5 metre wide optical telescope in New Mexico to conduct surveys over 20 years. Specifically, the map comes from the Baryon Oscillation Spectroscopic Survey (eBOSS), which is built to measure the expansion of the universe. Yesterday, 23 papers representing over 500 pages of new research were released.

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

To get a 3D map, you need three dimensions. The most difficult, explains Will Percival, the Director of the Waterloo Centre for Astrophysics at the University of Waterloo and a lead researcher on the team, is figuring out just how far these galaxies are from us.

“The difficulty lies in getting that third dimension, that distance to the galaxy. we do that by measuring the redshift of the galaxy, that is how fast the galaxy is moving away from us,” says Percival. “And we use the Hubble expansion of the universe to translate on that velocity through to a distance.”

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

Scientists have long known that the universe is constantly expanding as a result of the Big Bang, but the team behind this map has discovered that it is expanding faster than we previously thought, and there is no concrete explanation yet as to why that is.

According to the history revealed in the eBOSS map, the expansion of the universe began to accelerate six billion years ago and has continued to get faster ever since.

“That’s just really whacky because if you just have a standard theory that gravity is acting on matter, gravity is an attractive force it pulls things together and it would in general tend to decelerate the universe,” says Percival. “Which means there’s physics out there that we don’t know about.”

While there are theories, “none of them are really compelling.” According to Percival, the simplest mathematical explanation would be taking Einstein’s cosmological constant equation and change one sign in it to change the universe from static to make it accelerate. Mathematically, it’s a simple thing to do but when it comes to the physics it’s much more difficult to explain.

In particular, the eBOSS team’s measurement of the current rate of expansion of the universe, the previously mentioned Hubble’s Law, is about 10 per cent lower than the value found from distances to nearby galaxies. The mysterious invisible component in the universe we call “dark energy” has been thought to have something to do with this, but like many other phenomena in the universe it remains unexplained.

While this is the largest map to date, Percival hopes that the next generation of surveys will gather more galaxies and potentially solve this mystery by “really getting a handle on 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 galaxy survey. Percival is involved in both. He says that DESI is about twenty times faster than the Sloan telescope they used for this map and is possibly a few months away from starting depending on the ongoing pandemic.

“I should emphasize that this is a group collaboration, hundreds all around the world in every continent. Its been an incredible team resource and I’m so happy to see it come to fruition,” says Percival.

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2020-07-20 17:29:57Z
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