New Method Measures Spin of Black Holes -- a Key to Galactic Growth

The discovery of a new method of measuring the spin in supermassive black holes could lead to a better understanding of their ability to drive the growth of galaxies, according to those behind the finding.

"We know the black hole in the centre of each galaxy is linked to the galaxy as a whole, which is strange because black holes are tiny in relation to the size of a galaxy," lead researcher Chris Done of the Department of Physics at Durham University said in a press release. "This would be like something the size of a large boulder (10m), influencing something the size of the Earth."

According to researchers, the reason for black holes' incredible power lies in their ability to spit out extremely hot particles at high energies that then prevent intergalactic gases from cooling and forming new stars in the outer galaxy.

What is not clear, however, is why the jets are ejected into space in the first place, though Durham and his team believe their power is closely linked to the spin of the black hole from which they're derived.

For this reason, the scientists set about developing a new method of measuring this spin. The resulting technique, according to the study's authors, involves viewing optical, ultraviolet and soft X-rays generated by heat as the black hole feeds on its surrounding disc in order to determine the distance between the two. Next, because this distance depends on the speed at which a black hole spins (fast spinning black holes pull the disc in closer, according to the researchers), the team was able to use this measurement to determine what this is.

"Understanding this connection between stars in a galaxy and the growth of a black hole, and vice-versa, is the key to understanding how galaxies form throughout cosmic time," Done said, explaining that if a black hole is spinning, "it drags space and time with it and that drags the accretion disc, containing the black hole's food, closer towards it."

This, in turn, causes the balck hole to spin even faster, he explained, comparing the phenomenon to an ice skater performing a pirouette.

"By being able to measure the distance between the black hole and the accretion disc, we believe we can more effectively measure the spin of black holes," he said. "Because of this, we hope to be able to understand more about the link between black holes and their galaxies."