'Monster black holes' discovered at hearts of two colliding galaxies

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has recently imaged two colliding galaxies, collectively called Arp 299, located 134 million light-years away, and found monster black holes in the hearts of each galaxy.

NuSTAR has revealed that the black hole located at the right of the pair was actively gorging on gas, while its partner was either dormant or hidden under gas and dust. The findings are helping researchers understand how the merging of galaxies can trigger black holes to start feeding, an important step in the evolution of galaxies.

NuSTAR was the first telescope capable of pinpointing where high-energy X-rays are coming from in the tangled galaxies of Arp 299. Ann Hornschemeier said that odds are low that both black holes are on at the same time in a merging pair of galaxies as when the cores of the galaxies get closer, however, tidal forces slosh the gas and stars around vigorously, and, at that point, both black holes might turn on.

The study is published in the Astrophysical Journal. 

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