It's no secret that supermassive black holes are heartless beasts: These objects of immense gravity that let nothing escape, not even light, have fascinated astronomers since the early 20th century. While it's believed that so-called supermassive black holes lurk at the centre of most galaxies, including our own, there's still much we don't know about how they formed, or why, except to remind us of our own mortality.
Image: John Wise, Georgia Tech
But new research from an international team of scientists might have some answers to at least one of the critical questions — namely, how supermassive black holes, which range in size from millions to billions of solar masses, apparently formed very quickly in the early universe. Using computer simulations, the researchers found that these giants can grow incredibly fast if they can suck the life (read: Radiation) out of a nearby galaxy, disabling their host galaxy's ability to create stars. Essentially, a burst of radiation from a nearby galaxy breaks molecular hydrogen (H2) into atomic hydrogen, preventing new stars from forming. Instead, all of that unborn-starstuff collapses into a black hole, allowing it to quickly achieve its supermassive status. The team's findings were published today in Nature Astronomy.
"The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years — a blip in cosmic time," study co-author Zoltan Haiman, an astronomy professor at Columbia University, said in a statement. "A few hundred-million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected."
Though they were quite vulturous, early supermassive black holes had some standards, apparently. The researchers found that the neighbouring galaxy supplying the radiation had to be certain size and distance away from the black hole's host galaxy — though these cosmic energy sources could be smaller and closer galaxies than other studies estimated.
"The nearby galaxy can't be too close, or too far away, and like the Goldilocks principle, too hot or too cold," study co-author John Wise, an associate astrophysics professor at Georgia Tech, said. Having that perfectly sized galaxy is what can cause supermassive black holes to grow so rapidly — relatively speaking, of course.
By understanding how ancient black holes could have formed, we can get a better sense of what the universe was like long before our solar system existed. The team is already planning to follow up this research with a study on how the merging of millions of black holes and stars could have formed ancient giants.
"Understanding how supermassive black holes form tells us how galaxies, including our own, form and evolve, and ultimately, tells us more about the universe in which we live," lead author John Regan, a postdoctoral researcher Dublin City University, said.