The Mystery of Why Supermassive Black Holes 'Feed' on Stars Has Been Solved
We know that supermassive black holes are at the center of almost all galaxies, but they're still one of the biggest mysteries in the universe—especially when it comes to their feeding habits. It's a bit unnerving to say black holes 'feed,' but saying black holes 'flatten and warp stars before ripping them apart and sucking them in' isn't any more comforting. Back in November 2014, scientists picked up on a black hole feeding on a star and shooting out a giant jet of energy, an event called a 'tidal disruption flare' that may have unlocked the secret to how black holes regulate the growth of stars within a galaxy.
When a star passes too close to a black hole, the gravity of the hole starts to warp it and pull it in, eventually pulling the star apart and dragging all the pieces into the accretion disk, the circle of material that swirls around the edge of the black hole.
All that star material ends up creating bursts of energy, which make up the 'tidal disruption flare,' which produces X-ray, radio, ultraviolet, and all kinds of other radiation.
It turns out that the November 2014 tidal disruption was special, however—one of the key discoveries made included that the 'jet' of the supermassive black hole in question appeared to grow when it was feeding on the star. According to Dr. Dheeraj Pasham of MIT:
"This is telling us the black hole feeding rate is controlling the strength of the jet it produces. A well-fed black hole produces a strong jet, while a malnourished black hole produces a weak jet or no jet at all. This is the first time we've seen a jet that's controlled by a feeding supermassive black hole."
This discovery has led to a potential breakthrough in understanding how stars form within galaxies: in general, stars need extremely cold temperatures to form, but the superheated particles coming out of a supermassive black hole end up heating large regions around them. This means that for every star that's consumed, a black hole can temporarily stop the creation of new stars in the area. According to Pasham:
"If the rate at which the black hole is feeding is proportional to the rate at which it's pumping out energy, and if that really works for every black hole, it's a simple prescription you can use in simulations of galaxy evolution. So this is hinting toward some bigger picture."
It sounds like this 'bigger picture' is shaping up to be a galactic "Circle of Life."