Supermassive space snacks


SMALL PRINT:HOW DO supermassive black holes at the centres of galaxies grow?

They could be “eating” individuals from pairs of stars that get too close, according to a new study from the US.

Black holes are thought to be extremely dense objects in space that have enormous gravitational pull.

“Ordinary” black holes generally result from the collapse of a star, but so-called supermassive black holes at the centres of galaxies can contain masses of up to billions of stars.

The new study, out online this week in the Astrophysical Journal Letters, puts forward a theory that “binary stars”, which is a pair of stars that orbit each other, can act as food for supermassive black holes.

Because a binary star system is larger than a single star, it is likely to interact with the black hole more efficiently.

“The binary doesn’t have to get nearly as close for one of the stars to get ripped away and captured,” says researcher Ben Bromley.

Meanwhile, the remaining star from the binary pair gets flung off into space, he adds. “The hole peels off one binary partner, while the other partner – the hypervelocity star – gets flung out in a gravitational slingshot.”

Powerful telescopes would be required to confirm the theory.

The study raises interesting questions, according theoretical physicist Prof Peter Hogan from University College Dublin, who was not involved in the research.

“A binary star is considered because it is larger than a single star and is therefore more likely to be captured by the black hole,” he says.

“But what about even larger gravitationally bound systems of stars such as a galaxy or even a gravitationally bound system of galaxies? They too would be available for capture by the supermassive black hole.”