A super-supermassive black hole on the run


Astronomers have spotted an enormous fast-moving black hole that is likely the product of the collision of two smaller but still enormous black holes, writes Andrew Masterson.


Artist’s impression of the wandering black hole with optical and X-ray images of the real thing (inset).
CXC/M. Weiss; X-ray: NASA/CXC/NRAO/D.-C. Kim; Optical: NASA/STScI

Astronomers are chasing a rogue black hole with a mass 160 million times greater than the Sun.

The black hole, located 3.9 billion light years away, was first spotted by NASA’s Chandra X-ray Observatory. While most black holes are stationary, and sit at the centres of galaxies, this one is unusual because it is on the move.

It is also huge: so huge, in fact that one theory suggests it was formed when two smaller black holes – each one of them big enough to be classified as supermassive – collided.

It is possible that this collision is what set the resulting super-supermassive black hole on the move, a phenomenon astronomers call a “recoil”.

When the two smaller black holes crashed into each other they would have created gravitational waves that went out more strongly in one direction than in others. In line with Newton’s law, the newly minted black hole might have been pushed in the opposite direction to the trajectory of the waves.

The force generated to propel the black hole depends on the direction and rate of spin of the two smaller holes. An accurate assessment of the new black hole’s speed and momentum will yield, though retrospective calculation, strong information about these elusive variables.

The renegade black hole has been named CXO J101527.2+625911. If it was, indeed, formed by the merger of two smaller ones, it implies that their two host galaxies probably also merged. Indeed, NASA researchers report signs of disturbance in star clusters in the vicinity of their target.

A paper describing the black hole can be found on the preprint site axRiv.

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Andrew Masterson is an author and journalist based in Melbourne, Australia.