Scientists have produced the most accurate map of all matter in the universe

A massive effort by a massive international team of scientists has given us the most accurate map to date of all the matter in the universe. An international collaboration has combined data from two major studies to reveal where the universe does and does not store its garbage – not only the ordinary matter that makes up planets, stars, dust, black holes, galaxies, but also dark matter. good: a mysterious invisible mass that creates more gravity than ordinary matter can explain.

The resulting map, which shows where matter has accumulated over the 13.8 billion years of the universe, will be a valuable reference for scientists trying to understand how the universe developed. Indeed, the results show that matter is not distributed as we thought, suggesting that something may be missing in the current Standard Model of cosmology. According to modern models, at the time of the Big Bang, all matter in the universe was condensed into a singularity: a single point of infinite density and extreme heat that suddenly exploded and expelled quarks quickly coalesced into a soup of protons. , neutrons and nuclei. Hydrogen and helium atoms appeared a few hundred thousand years later; The entire universe was created from them.

How these early atoms spread, cooled, clung together and formed stars, rocks, and dust is the detective work behind what the universe around us looks like today. One of the main clues we use is where all the matter is now, because scientists can work backwards to understand how matter got there. But we can’t see them all. In fact, most of the matter in the universe – about 75 percent – is completely invisible to our current detection methods.

We detect this only indirectly because it creates gravitational fields that are stronger than they should be for the normal amount of matter. This shows up in phenomena like galaxies spinning faster than they should and a little quirk of the universe we call gravitational lensing. When something in the universe — like a cluster of thousands of galaxies — has enough mass, the gravitational field around it becomes strong enough to affect the curvature of space-time itself.

This means that any light passing through this region of space will travel along a curved path, causing the light to be distorted and magnified. These lenses are also stronger than they would have been if it made them ordinary matter.

To map the matter in the universe, the researchers compared gravitational lensing data collected by two different studies: the Dark Energy Survey, which collects data at wavelengths in the ultraviolet, visible, and near-infrared ranges; and the South Pole Telescope collecting data on the cosmic microwave background, the faint trace of radiation from the Big Bang.

By cross-comparing these two datasets obtained by two different tools, researchers can be much more confident in their results.

“It acts as a cross-validation, so it becomes a much more reliable measurement than if you were using one or the other,” said astrophysicist Chihwei Chang of the University of Chicago, who is the lead author of one of the three papers. business.

The lead authors of the other two papers are physicist Yuki Omori of the Kavli Institute for Cosmological Physics and the University of Chicago, and telescope scientist Tim Abbott of the Cerro Tololo Inter-American Observatory NOIRLab. The resulting map, based on galaxy locations, galaxy lenses, and cosmic microwave background lenses, can be predicted to understand the distribution of matter in the universe.

This map can then be compared with models and simulations of the evolution of the universe to see if the observed distribution of matter agrees with theory. The researchers made some comparisons and found that their maps were mostly consistent with existing models. But not exactly. There was little difference between observation and prediction; The researchers found that the distribution of matter was less complex, more uniform than the models had predicted.

This shows that our cosmological models can change.

This is hardly surprising – there are a few inconsistencies between cosmological observations and theory that suggest we’ve missed an admission or two somewhere; and the team’s findings are consistent with previous studies, but the more accurate and complete our data, the more likely these discrepancies will be resolved.

There is still a lot of work to be done; results are still uncertain. Adding additional surveys will help refine the map and validate (or invalidate) the team’s conclusions. And of course the map itself will help other scientists conduct their own investigations into the mysterious and uncertain history of the universe.