A new survey of more than 100 galaxies by NASA’s Chandra X-ray Observatory has uncovered signs that black holes are demolishing thousands of stars with one crucial goal: gaining more mass.
The study used Chandra data from dense star clusters at the centers of 108 galaxies, searching for evidence of where and how these medium-sized black holes might emerge and expand.
“When stars are close together like in these extremely dense clusters, they provide a viable breeding ground for intermediate-mass black holes,” said Vivienne Baldassare of Washington State University in Pullman, Washington, who led the study. “And it seems that the denser the star cluster, the more likely it is to contain a growing black hole .”
Analyzing a hundred galaxies
After surveying 108 galaxies, they selected 29 of them that they observed with Chandra. Of these, the group published images of four such galaxies, NGC3344, NGC 6503, NGC 1385 and NGC 1566. Each image was captured by the Hubble Space Telescope and then overlaid with images from Chandra. The result is a collage of galaxies with growing black holes. X-rays from Chandra (blue) have been superimposed on optical images from NASA’s Hubble Space Telescope of these galaxies.
According to the study, if the density of stars in a cluster is above a threshold value, a stellar-mass black hole in the center of the cluster will undergo rapid growth as it approaches, crushes, and ingests nearby stars . The density threshold also depends on how fast the stars in the clusters are moving.
“This is one of the most spectacular examples we’ve seen of the insatiable nature of black holes, because thousands or tens of thousands of stars can be consumed during their growth,” said Nicholas C. Stone, co-author of the paper. “The runaway growth only starts to slow down once the supply of stars starts to run out.”
stellar mass black holes
Thus, the black holes responsible for this destruction would be stellar mass holes and would be fed by what astronomers call “uncontrolled growth”. Stellar-mass black holes are the smallest type discovered so far. They are typically 5 to 30 times the mass of the Sun. However, when they grow out of control, astronomers believe they become “intermediate-mass black holes.”
The process suggested by the Chandra survey results can occur at any time in the history of the universe , implying that intermediate-mass black holes can form billions of years after the Big Bang, right up to the present day.
Referencia: Vivienne F. Baldassare et al, Massive black hole formation in dense stellar environments: Enhanced X-ray detection rates in high velocity dispersion nuclear star clusters. arXiv:2203.02517 [astro-ph.HE] arxiv.org/abs/2203.02517
