Scientists reveal the most detailed 3D map of the universe EVER

The largest and most detailed 3D map of the universe ever created has been unveiled, bringing an end to a five–year–long scientific marathon.

This week, the 5,000 fibre–optic eyes of the Dark Energy Spectroscopic Instrument (DESI) locked onto a patch of sky near the Little Dipper.

Those observations were the last pieces of a jaw–droppingly large ‘CT scan’ of the universe, which scientists have been slowly patching together since 2021.

Altogether, the DESI survey captures more than 47 million galaxies and 20 million additional stars.

This brings together observations for more than six times as many galaxies and quasars, bright signals from black holes, as all previous measurements combined.

The light from the most distant galaxies is over 11 billion years old, almost stretching back to the birth of the universe.

Dr Seshadri Nadathur, a researcher from the University of Portsmouth and co–chair of DESI’s galaxy and quasar clustering working group, says: ‘It is hard to overstate how important this DESI map of galaxies will be for cosmology.

‘We’ve barely scratched the surface so far, and I’m excited to see what else we can learn.’

Every night for the last five years, each of DESI’s 5,000 eyes has locked onto a different pinprick of light in the sky.

Robotic arms lined up each fibre–optic lens within an accuracy of 10 microns, or less than the width of a hair, locking onto a new spot every 20 minutes.

The light they gathered was measured and split into its constituent colours by ten spectrographs to reveal each object’s position, velocity, and chemical composition.

The result is a 3D map of the universe around Earth of baffling detail, precision, and scale.

The only areas hidden from the survey are the areas of sky where the thick edge of the Milky Way blocks out light from more distant stars, visible as the black wedges on the map.

The DESI collaboration, which involved over 900 scientists from 70 institutions around the world, was created to unlock the secrets of dark energy.

This is the invisible force that makes up about 70 per cent of the universe and is responsible for its accelerating expansion.

Data from the survey’s first three years showed that dark energy, once considered to be a constant, might actually be changing.

Since the birth and eventual death of the universe depend on the balance between matter and dark energy, this revolutionary discovery had the potential to upend everything scientists believed about the cosmos.

Now, with even more data than ever before, scientists are hoping that the full map will show whether dark energy’s apparent evolution is bigger or smaller than they thought.

The collaboration will immediately begin processing the completed dataset, with the first dark energy results from DESI’s full five–year survey expected in 2027.

Incredibly, DESI finished its observations ahead of schedule and gathered far more data than scientists had expected.

The original plan had been to observe 34 million galaxies and quasars.

However, the scan proved so efficient that astronomers had enough time to revisit the same areas multiple times, revealing yet more detail.

Dr Michael Levi, DESI director and a scientist at Berkeley Lab, says: ‘DESI’s five–year survey has been spectacularly successful. The instrument performed better than anticipated.

‘We’re going to celebrate completion of the original survey and then get started on the work of churning through the data, because we’re all curious about what new surprises are waiting for us.’

Starting from 2028, scientists plan to grow the surveys’ area by about 20 per cent to cover 17,000 square degrees of sky.

For comparison, the moon covers just 0.2 square degrees, while the full sky spans over 41,000 square degrees.

DESI will need to push closer to the crowded plane of the Milky Way and further south, where more of Earth’s atmosphere is in the way.

This will make gathering new observations considerably more difficult, but the scientists behind the project are optimistic that their instrument is up to the task.

Scientists will use DESI to go over previously mapped areas to look for a new class of galaxies known as ‘luminous red galaxies’.

The researchers will also study nearby dwarf galaxies and stellar streams, bands of stars torn from smaller galaxies by the Milky Way’s gravity, in the hope of learning more about dark energy.

Stephanie Juneau, associate astronomer and NSF NOIRLab representative for DES, says: ‘Ultimately, we are doing this for all humanity, to better understand our Universe and its eventual fate.

‘After finding hints that dark energy might deviate from a constant, potentially altering that fate, this moment feels like sitting on the edge of my seat as we analyse the new map to see whether those hints will be confirmed.’

WHAT IS DARK ENERGY?

Dark energy is a phrase used by physicists to describe a mysterious ‘something’ that is causing unusual things to happen in the universe. 

The universe is full of matter and the attractive force of gravity pulls all matter together. 

Then came 1998 and the Hubble Space Telescope observations of very distant supernovae that showed that, a long time ago, the universe was actually expanding more slowly than it is today.

So the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating. 

No one expected this, no one knew how to explain it. But something was causing it.

‘The universe is not only expanding, but it is expanding faster and faster as time goes by,’ Dr Kathy Romer, scientist at the Dark Energy Survey told MailOnline.

‘What we’d expect is that the expansion would get slower and slower as time goes by, because it has been nearly 14 billion years since the Big Bang.’