Astronomers present map of dark matter distribution in the universe

Using observations from the James Webb Space Telescope on a patch of sky covering nearly three times the area of ​​the full Moon, scientists have produced the most detailed cosmic map yet of the mysterious substance known as dark matter, which makes up most of the matter in the universe.

Ordinary matter builds stars, planets, people and everything else we can see. However, it only makes up about 15 percent of the total matter in the universe. The rest is dark matter, which neither emits nor reflects light, making it invisible to the human eye and telescopes, Reuters reports.

Scientists infer its existence based on the gravitational effects it exerts on large scales, such as the speed of rotation of galaxies, the way galaxy clusters are interconnected, and the bending of light from distant objects as it passes through massive cosmic structures.

The new map of the distribution of dark matter is based precisely on this phenomenon of light bending, which causes subtle distortions in the shapes of about 250.000 distant galaxies observed with the Web, thanks to the gravitational influence of matter along the line of sight.

The previous map of dark matter was based on observations from the Hubble Space Telescope. The new map, thanks to the increased capabilities of the Web, offers twice the resolution of the previous one, covers larger parts of the cosmos and penetrates deeper into the past - practically to the period of about eight to ten billion years ago, which is crucial for the formation of galaxies.

"This allows us to resolve finer structures of dark matter, detect previously unseen mass concentrations, and extend the mapping of dark matter to earlier epochs of the universe," said observational cosmologist Diana Sconjamiljo of NASA's Jet Propulsion Laboratory in California, lead author of the research published in the journal Nature Astronomy.

The map reveals with unprecedented clarity new details of the macrostructure of the universe known as the cosmic web - galaxy clusters, vast filaments made of dark matter along which galaxies and gas are distributed, as well as regions with lower mass density.

Webb, an infrared telescope that has about six times the light-gathering power of Hubble, was launched in 2021 and has been operational since 2022.

"The James Webb Space Telescope is like putting new glasses on the universe," said Sconamiglio.

"It sees fainter and more distant galaxies with much sharper detail than ever before. This essentially gives us a much denser network of background galaxies to work with, which is exactly what is needed for this kind of research. More galaxies and sharper images directly translate into a sharper map of dark matter."

The map covers a section of the sky known as the Cosmic Evolution Survey, or COSMOS, which is located in the direction of the constellation Sextant. The researchers say the map will enable future exploration of the universe in a number of ways.

"For example, one of the key questions in astrophysics is how galaxies grow and evolve over time - how the universe went from an almost perfectly homogeneous 'soup' to the spectacular diversity of galaxies we observe today," said observational cosmologist and study co-author Jacqueline McCleary of Northeastern University in Boston.

"Dark matter halos - self-gravitating 'clouds' of dark matter - are the birthplaces of galaxies, the nurseries of galaxies. So knowing where dark matter is, how much of it there is, and relating that data to the population of galaxies within the dark matter distribution is an important constraint on models of galaxy formation and evolution," said McLeary.

The method the researchers used, which is based on the bending of light, revealed the distribution of both dark and ordinary matter.

The researchers said their observations are consistent with the leading cosmological model, known as Lambda-CDM, or the cold dark matter model, which explains the origin of the universe through the Big Bang and its subsequent evolution and structure. According to this model, the universe is dominated by dark matter and an invisible cosmic force known as dark energy, which is responsible for the accelerated expansion of the universe.

"In this framework, dark matter represents the gravitational backbone on which galaxies, groups and clusters form, creating a large-scale cosmic network. Our map provides a much sharper observational insight into this dark matter 'scaffolding'," said Skonjamiljo.