Astronomers discovered a black hole that roams alone in space

Astronomers have discovered a black hole that wanders solitary in space. It is an enormous object that has left the center of its galaxy and is now roaming in space at a speed of 5.6 million km/h. If you’ve never heard of a runaway SMBH, you’re not alone. SMBHs are normally locked into place at the centers of galaxies, and that’s where they stay. But scientists think that in rare circumstances SMBHs can escape their galaxies. In its wake, this cosmic monster would be dragging a long strand of stellar gas. That’s how scientists were able to detect it.

An illustration of how the black hole has moved away from the center of its galaxy. Credit: van Dokkum et al

The gas trail is twice as long as our galaxy. Using observations from the Hubble Space Telescope, astronomers found a fine line from the center of a galaxy. Comparing the data with another telescope, the Keck of Hawaii, they deduced that it was a supermassive black hole literally expelled from its galaxy, leaving behind a long trail of gas and newly formed stars.

That galaxy is 7.5 billion light-years away. Like most other galaxies, it probably had a supermassive black hole at its center. However, the thin line observed by Professor van Dokkum and his team did not have the same characteristics as a jet of black hole. The best explanation, in brief, is that this cosmic monster is moving through the gas that surrounds its native galaxy.

Well, how did it happen? The best explanation is "a three-body interaction". In summary, two black holes in gravitational equilibrium are disturbed by the mass of a third black hole. It is rare that there are three black holes in a galactic center, but if it is one born from the fusion of two or more galaxies, then it is possible. After a period of gravitational instability among the three black holes, in the new state of equilibrium, one of the "original" black holes was probably ejected from the galactic center.

References: Universe Today