The black hole feeding on its own galaxy

By Kaylin Li

Somewhere far, far away, a 13 billion-year-old black hole is eating away at its galaxy.

This finding was released in an early access paper on Jan. 17 in Nature, in which researchers analyzed data from the James Webb Space Telescope (JWST). You might recall that JWST also produced the first-ever image of a black hole in 2017. Now, by analyzing the spectral data from JWST images, researchers have found a black hole in the galaxy GN-z11 — currently the oldest black hole we have ever found, and with a mass of 1.6 million suns.

This black hole is now challenging current theories of black hole formation. Based on current theories, the black hole would have taken longer than it has ever existed to become this size. Black holes “eat” and grow by pulling in dust, gas, and other materials, forming a glowing disk around it that is detectable by telescopes like JWST. While the actual black hole usually can’t be captured in images, these accretion disks are what appear in images and are the tell-tale sign of black holes.

But black holes can get full too — if a black hole eats too quickly, beyond what is called the Eddington rate, this disk heats up and can blow away, which limits the black hole’s growth.

Given the data, though, the black hole was growing at five times the Eddington rate. This meant that the black hole was eating much faster than was expected. “This black hole is essentially eating the [equivalent of] an entire sun every five years,” study author Robert Maiolino told NPR. “It’s actually much higher than we thought could be feasible for these black holes.”

There are a few prevailing theories that could explain this. One theory, the heavy-seed theory, is that the black hole was born massive — perhaps from the “sudden collapse of giant gas clouds” or “many mergers between clumps of stars and black holes,” all of which have enough mass and energy involved to form larger-than-normal black holes. These scenarios might require another nearby galaxy or black hole producing enough photons to enrich the gas clouds so that the clouds get big enough to collapse into black holes instead of stars.

Another theory is that the black hole could have super-Eddington phases, where black holes can temporarily exceed the Eddington rate before slowing down again.

Either way, as the black hole grows, it could be spelling doom for its host galaxy, and itself. Black holes emit energy as they feed, and if the black holes eat too fast, the energy emitted could sweep away the gas of its galaxy GN-z11. There might not be enough gas for new stars to form, and as the existing stars die, the galaxy dies. This would also leave the black hole with no material to eat and kill the black hole as well.

Researchers hope to find more and older black holes to better investigate their formation and give us a better understanding of space.