Overview

Astrophysicists are searching every possible corner of the universe trying to unravel the mysteries that shroud the cosmos — and they are using every technology at their disposal to do so. These attempts have revealed the overall mass and energy densities of the cosmos, allowing cosmologists to map the universe on a large scale.

It turns out that ordinary matter is just a tiny part of the cosmos. Everything we can see — you, me, animals, trees, planets — makes up less than 5% of the universe. Some 20% of the universe is a mysterious substance known as “dark matter.” The most abundant thing in all the universe? An unknown form of energy that rapidly stretches, tears, and expands the fabric of space-time. It’s called “dark energy,” and it makes up more than 70% of the universe.

A new effort to understand this dark energy has managed to reconstruct a three-dimensional map of the observable universe. It’s the most detailed 3D map to date. And the result is fascinating.

The science and other stuff to know

In the mountainous lands of Arizona is the Kitt Peak National Observatory, where astrophysicists and cosmologists work observing the night sky. One of its instruments is dedicated to observing deep space to collect data to study the nature, effects, and distribution of dark energy. As mentioned, this is a type of energy unknown to scientists that is responsible for the accelerated expansion of the universe.

The Dark Energy Spectroscopic Instrument (DESI) became operational in mid-2021 and has already collected enough spectroscopic data to model a 3D map of the observable universe in enormous detail. DESI will continue to scan the night sky for at least another four years. It is expected that, by 2026, it will have mapped more than 35 million galaxies.

Slice of 3D map modeled from DESI observations

In the images of the 3D model, two structure distribution cones can be seen. This is because we aren’t able to see the entire universe, as the dense galactic center does not allow us to see the structures behind it. We may have to wait 175 million years — the time it will take for the Sun to travel to the opposite side of the galactic disk — to complete the map.

So what?

Cosmologists still don’t understand why there is such a thing as dark energy, and they don’t know the full shape of the universe. This ignorance means we can’t make accurate predictions about the future of the cosmos. It could well be that it expands infinitely and all the matter in it disintegrates and cools, causing a stage that physicists have called “Big Freeze.” Another possibility is that the expansion stops for some reason linked to the exotic nature of dark energy, and gravity begins to concentrate matter, causing a “Big Crunch:” a collapse antagonistic to the Big Bang.

The data provided by DESI will help cosmologists understand how dark energy operates in the expansion dynamics and predict the future of the universe.

What’s next?

The team notes that, that in the coming years, they will be able to improve the dynamic models of galaxy formation and large-scale structures, thanks to the data provided by this instrument. They also explain that they will be able to more accurately map the distribution of dark matter in galactic clusters. In this respect, DESI continues to measure the expansion rate of the universe and refine the current cosmological model. Prof Carlos Frenk from the Institute for Computational Cosmology said DESI’s data will ultimately “help uncover some of the most intimate secrets of the cosmos.” “We will also learn more about dark matter and the role it plays in how galaxies like the Milky Way form and how the universe is evolving,” he said to the BBC.