There may be hundreds of millions of small black holes distributed in galaxies, but they are quieter than supermassive black holes, and scientists want to see them more difficult than supermassive black holes. However, recently an international team analyzed the Pa Roman 5 star cluster located in the Milky Way, and found that there may be hundreds of stellar black holes clustered inside.
The Palomar 5 star cluster is one of about 150 globular star clusters orbiting the Milky Way. It is over ten billion years old and is about 80,000 light-years away from us. However, due to the gravitational force of the Milky Way, the star cluster is actually disintegrating. Many stars are leaving the cluster along two stellar streams, which have a mass about 5,000 times the mass of the sun and extend 30,000 light-years in length.
Astronomers have successively discovered about 30 star streams in the Milky Way’s halo. This is a chain structure composed of many stars moving around the galaxy along a long and narrow orbit. Astronomers are not yet sure about how star streams are formed. The main theory is It is believed that globular star clusters or dwarf galaxies were torn apart by nearby large galaxies by tidal action.
However, none of the recently discovered star streams seemed to find related star clusters, which made astronomers suspicious. In order to understand these star streams, the team of the University of Barcelona in Spain decided to study the Paloma 5 star cluster. The number of invisible black holes in a star cluster is a big variable in the simulation process, but the team has developed a new method that only needs to look at the orbit of each star from the formation of the cluster to the final ejection, and change the properties of the cluster to find a match that matches the observations. Situation, we can understand how many black holes there are in the cluster.
The simulation results show that the Paroma 5 star cluster may contain hundreds of black holes with a mass of 20%. Because the total mass of the black hole is so large, the star disappears faster than the black hole, which causes the star cluster to expand and its tail becomes longer. It is estimated that stars will be ejected by black holes one after another in the next 1 billion years, and eventually only black holes will remain in the star cluster.
The researchers pointed out that there may be a large number of black holes in all star clusters that form star streams. This is very important for us to understand the formation of globular star clusters, the initial mass of stars, and the evolution of massive stars.
The new paper was published in the journal Nature Astronomy.
(The first picture is a schematic diagram, source: Pixabay)
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