14 DAY TRIAL // One of the greatest mysteries in the fields of astronomy and astrophysics was until recently figuring out how supermassive black holes get so big. These impressively-large formations can be found at the cores of equally-massive galaxies, and they can grow continuously until their reach masses a billion times larger than that of the Sun. For many years, various explanations have been proposed and dismissed, but now a new idea appears to hold up to thorough scientific scrutiny.
It's a widely-known fact that black holes grow by accumulating mass from their surroundings. They attract various materials, such as cosmic gas and dust, in their surroundings, and then make them a part of their accretion disks. These are the circular structures that can be found around most large black holes, from which the dark behemoth continuously draws matter. But, in the case of gas being gobbled up by these structures, astrophysicists ran into a dilemma, PhysOrg reports.
The gas has a large angular momentum, which means that it basically moves too fast to allow for the black holes to trap it into their accretion disks. So experts have been pondering on the mechanisms the formations employ in slowing the gas down sufficiently. University of California in Berkeley (UCB) astrophysicists Philip Hopkins and Eliot Quataert recently published a new study, in which they propose that old lopsided stellar disks, such as the one noticed around the black hole at the core our neighboring galaxy, Andromeda, may play a pivotal part in slowing down the swirling gas.
These disks can grow to a diameter of dozens of light-years, and, due to their lopsided nature, they tend to exert an uneven gravitational attraction on the incoming gas. This in turn causes various gas filaments within the larger clouds to collide with each other, creating friction, and reducing speed sufficiently to allow for the black hole that traps the gas with its own gravitational pull. In spite of popular belief, the dark behemoths can only gobble up gas if it passes within one light-year of their event horizon. Through this mechanism, the investigators propose, a black hole such as Andromeda's could gain several solar mass-worth of matter each year, helping to account for its current mass.