Scientists have measured a fundamental property of a supermassive black hole – how fast it turns – measuring a star that slams into it
It can be difficult to measure black holes unless they actually do something, like when they slam together or throw up matter jets. But the scientists behind the new result were able to measure the mass and rotation of a rather massive black hole, demonstrating that these short stellar events, called tidal interruption events, could offer another way to understand black holes.
have already been measurements of spin from actively growing black holes, "or by acquiring more matter under the influence of gravity, the first author of the study Dheeraj Pasham, Einstein Postdoctoral Fellow at the MIT Kavli Institute, said Gizmodo. "This measure is different, in the sense that we were able to measure the rotation of a black hole that was dormant", at least until the tide break event.
An automatic detection of the sky called All -Sky Automated Survey for SuperNovae, or ASASSN, detected the flash on November 22nd, 201
Scientists used these X-ray emissions to infer the mass and rotation of the black hole. And in this case, the researchers estimated that the mass was between a few hundred and ten million times the mass of the Sun, and the spin was an incredible 50 percent of the speed of light, according to a results-based MIT release of the document, published yesterday in Science.
Pashnam warned that these values are still based on a model and that there may be more ways to interpret the same data. And this is just a data point, so you should not think so much about the spin and mass values yet. Instead, the document demonstrates an important new way of measuring the properties of all black holes, not just a special series of them.
A researcher not involved in the study, James Guillochon, ITC Fellow at the Harvard-Smithsonian Center for Astrophysics, agreed. "Their results seem to be consistent with other works (especially previous works on [ASASSN-14li] but they also work on supermassive spin of the black hole)," he told Gizmodo. "Their result suggests that tidal interruption events should be followed regularly by X-ray telescopes to maximize our knowledge of their properties."
This is indeed the goal, Pasham told Gizmodo. He explained that these tidal disruption events occur every thousand or 10 thousand years for the galaxy, so they hope that one day they can measure several hundred of these events in the year to get a general picture of the properties of the black hole.
And there's no need for concern: our star will not be one of those that will slam into a supermassive black hole anytime soon.