Star clusters point to supermassive black holes kicked from host galaxies

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Washington, July 10 (ANI): A new research has determined that the tight cluster of stars surrounding a supermassive black hole after it has been violently kicked out of a galaxy represents a new kind of astronomical object and a fossil record of the kick.

The research, published in The Astrophysical Journal discusses the theoretical properties of "hypercompact stellar systems" and suggests that hundreds of these faint star clusters might be detected at optical wavelengths in our immediate cosmic environment.

Hypercompact stellar systems result when a supermassive black hole is violently ejected from a galaxy, following a merger with another supermassive black hole.

The evicted black hole rips stars from the galaxy as it is thrown out.

The stars closest to the black hole move in tandem with the massive object and become a permanent record of the velocity at which the kick occurred.

"You can measure how big the kick was by measuring how fast the stars are moving around the black hole," said David Merritt, from Rochester Institute of Technology.

"Only stars orbiting faster than the kick velocity remain attached to the black hole after the kick. These stars carry with them a kind of fossil record of the kick, even after the black hole has slowed down. In principle, you can reconstruct the properties of the kick, which is nice because there would be no other way to do it," he added.

"Finding these objects would be like discovering DNA from a long-extinct species," added Stefanie Komossa, from the Max-Planck-Institut for Extraterrestrial Physics in Germany.

The best place to find hypercompact stellar systems is in cluster of galaxies like the nearby Coma and Virgo clusters, according to the researchers.

These dense regions of space contain thousands of galaxies that have been merging for a long time. Merging galaxies result in merging black holes, which is a prerequisite for the kicks.

"Even if the black hole gets kicked out of one galaxy, it's still going to be gravitationally bound to the whole cluster of galaxies," Merritt said. "The total gravity of all the galaxies is acting on that black hole. If it was ever produced, it's still going to be there somewhere in that cluster," he added.

Merritt and his co-authors think that scientists may have already seen hypercompact stellar systems and not realized it.

These objects would be easy to mistake for common star systems like globular clusters. (ANI)

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