It is estimated that about 10–20 percent of the mass of galactic clusters is occupied by visible (baryonic) matter, which consists of stars and hot plasma. The rest is occupied by dark matter, which cannot be detected by our instruments. For the first time, the separation of two types of matter has been directly observed in the merging galactic clusters MACS J0018.5 +1626.

Galaxy clusters contain thousands of objects held together by gravity. They are huge formations in the universe that contain dark matter as well as lots of hot gas that glows in the X-ray spectrum.

MACS J0018.5+1626 is a merging pair of galaxy clusters billions of light-years away. Scientists from the California Institute of Technology (USA) observed it using data from their submillimeter observatories, the WM Keck Observatory, the ASTE submillimeter antenna, and the X-ray Observatory. Chandra, space telescopes Hubble’sAnd HisA complete analysis of all the information required several years.

Two galactic clusters collided like dump trucks of sand, in which dark matter played a role. The cargo was scattered around during the collision. This analogy was made by Emily Silich, the first author of the study published in the publication. Astrophysics Journal.

During the collision, individual galaxies in the clusters were not damaged because they had too much “air” and the gas clouds filling the space between them were overheated by creating vortices. The electromagnetic forces that ordinary matter experiences slow down and trap the gas during the collision. The dark matter clumps, which only react to the gravitational pull, were further filtered out. In this way, ordinary and dark matter were separated from each other.

The most famous example of this separation of two types of matter is the Spheres galactic cluster. Only the merging MACS J0018.5+1626 (now called MACS J0018.5) has a slightly different orientation from Couli, with a rotation of about 90 degrees. One of the clusters in MACS J0018.5 appears to be flying almost directly towards Earth, while the other appears to be rapidly receding. This provided a good overview and allowed the velocities of dark and ordinary matter to be mapped for the first time during a collision.

The researchers used a method known as the Sunyaev Zeldovich kinetic effect, which manifests itself in the change in brightness of remnant photons due to electrons scattering off them in hot gas moving toward Earth. It is used to measure the speed of intergalactic gas in clusters.

Professor Jack Sayres, who led the research, observed the Sunyaev-Zel’dovich effect in the discrete galaxy cluster MACS J0717 in 2013. For the object MACS J0018.5, it was first used even earlier in 2006.

Scientists have previously measured the speed of gas in various galaxy clusters using the Sunyaev-Zeldovich effect. They then determined the speed of the galaxies in the clusters, which provided an indirect estimate of the speed of dark matter. Now it’s time to look at the orientation of MACS J0018.5. The scientists also mapped the dark matter in the cluster using gravitational lensing and simulated its own collision.

It turned out that the galaxies were moving towards each other at a speed of about 3,000 kilometers per second. This is about one hundredth of the speed of light. Once astronomers saw the whole picture, they saw that dark matter and ordinary matter were separated and moving in different directions. Thanks to this study, researchers have a tool to directly study dark matter, which still remains a mystery.