The closest cluster to Earth is being torn apart by dark matter
Something strange is happening in the galaxy.
According to the latest data analysis of the Gaia satellite, the closest cluster to the solar system is being torn apart — not only a normal phenomenon, but also the gravitational pull of some kind of invisible massive object.
Astronomers say the damage may have hinted at dark matter nearby, causing a gravitational catastrophe to the surroundings.
In fact, it is inevitable that the cluster will be torn apart by gravity. Star clusters, as the name suggests, are made up of many stars that come together by gravity. Inside the cluster, gravitational interactions are rather chaotic.
Under the influence of internal gravity and the forces of the external Galactic tides, the cluster was eventually torn apart into galaxies: what is known as the tidal current.
These tides are difficult to see in the sky because measuring the distance of stars is tricky, so the stars are gathered together to see. However, gaia satellites are drawing the most detailed and accurate three-dimensional maps of the Milky Way, and measuring as many accurate position and rate data as possible for stars.
Because the stars torn apart from the clusters still have the same rate (more or less) as the protoclamations, the Gaia data helps astronomers identify many previously unknown tidal currents, as well as clusters with tides — where the tails of stars have begun to loosen from front to back.
In 2019, astronomers revealed that in the second Gaia data, they found evidence of the tidal wake of the Bixing Cluster, which is the closest cluster to Earth at a distance of 153 light-years.
This caught the attention of astronomer Theresa Yellabkova and her colleagues at the European Space Agency and the European Southern Observatory. When versions 2.5 and 3 of the Gaia Data were received, they began to expand the search parameters to capture the stars that had been missed by earlier detections.
They found hundreds of stars associated with the Bi star cluster. The diameter of the cluster's center is about 60 light-years, and the tail of the tide spans thousands of light-years.
It's normal for a star cluster that has been damaged by galactic tidal forces to have such a tail, but the team noticed something strange. They simulated a cluster rupture and found more stars in the tail part of the simulation. In real clusters, many stars are missed.
The team did more simulations in an attempt to find what caused the star to deviate from the right path — being able to reproduce the observed phenomenon when the gravitational action of an object with a mass 10 million times larger than the sun.
"There must have been a close interaction with this massive galaxy cluster, and the Bixing Cluster has just been crushed," Yellabkova said.
The biggest problem with this situation is that nothing is currently seen near this cluster. However, the universe is full of unseen things—dark matter, and naming this mysterious substance can only be inferred from its gravitational effect on the matter we can see.
Based on these gravitational influences, scientists calculate that about 80 percent of the matter in the universe is dark matter. Dark matter is thought to be an important part of galaxies — large amounts of matter from the early universe came together to form the galaxies we see today.
Today these clusters of dark matter can still be found in the "dark halo" around the galaxy. There is a faint halo in the Milky Way that is 1.9 million light-years in size. Among these halos, astronomers predict denser clumps, called dark matter sub-halos, that float only around.
Future searches may uncover a structure that could cause the stars at the tail of the Bizet cluster to disappear, without which the researchers believe this disruption could be the effect of a dark matter sub-halo
The discovery also suggests that tidal currents and tails could be excellent places to search for mysterious sources of gravitational interactions
Yellabkova said: "With Gaia, the way we see the Milky Way has completely changed".
"With these foundations, we will be able to map the substructures of the Milky Way better than ever before."
The study was published in Astronomy and Astrophysics.
Related knowledge
In cosmology, dark matter is matter that does not interact with electromagnetic forces, that is, does not absorb, reflect, or emit light. People can only know through the effects of gravity, and a large amount of dark matter has been found in the universe. Modern astronomy detects dark matter through methods and theories such as gravitational lensing, the formation of large-scale structures in the universe, and microwave background radiation.
BY: sciencealert
FY: Lan Wu
If there is any infringement of the relevant content, please contact the author to delete it after the work is published
Please also obtain authorization for reprinting, and pay attention to maintaining completeness and noting out