Most distant black hole discovered, but it's "impossibly massive"
Astronomers have discovered the most distant – and therefore earliest – known black hole. Hiding in a galaxy called GN-z11, this black hole is bigger than should be possible given the age of the universe.
GN-z11 lies about 32 billion light-years away from Earth, and for a while after its discovery in 2016 it was the most distant known galaxy. Before you rush to the comments to say that that distance is impossible, and nothing can be farther than 13.8 billion light-years – the age of the universe – remember that the universe is expanding at an accelerating pace, so there is now more space between us and the galaxy than there was when the light left it.
Anyway, to get a good look at this distant galaxy, astronomers have now used the powerful, infrared eye of the James Webb Space Telescope. They managed to detect the hot, ultraviolet glow of an accretion disc – the swirling dust and gas that gives away the presence of a supermassive black hole. That makes it comfortably the most distant black hole ever observed, and judging by its size the team would estimate its age to be about a billion years.
That raises a major problem. Thanks to the constraint of the speed of light, we’re seeing GN-z11 as it was 13.4 billion years ago, or just 400 million years after the Big Bang. The universe literally isn’t old enough at this point for that black hole to exist yet.
This suggests our models of how black holes form and grow might need some tweaking. Proposed alternatives are that they formed from the collapse of huge gas clouds, which leaves them with more mass right from the beginning and giving them a head start on growth – so-called “Outsize Black Holes.” Other ideas suggest black holes with more matter nearby can feed and grow faster than we currently give them credit for. Or, both of these models could be at work together.
“It’s very early in the universe to see a black hole this massive, so we’ve got to consider other ways they might form,” said Professor Roberto Maiolino, lead author of the study. “Very early galaxies were extremely gas-rich, so they would have been like a buffet for black holes.”
This isn’t the first object James Webb has discovered that seems to be too advanced for its age. The telescope has already spotted a series of “impossibly” huge galaxies that were found to house more mass than the entire universe was thought to contain at that time. Others exhibited Milky Way-like bar structures earlier than models say they should have developed.
Astronomers are scrambling to explain the results, proposing everything from galaxies going through “starburst” phases, to hypothetical stars powered by annihilating dark matter that just look like galaxies at that distance. Others are even going as far as to suggest that the universe might be twice as old as we thought.
Only further observations will help unravel what’s turning out to be a major cosmological conundrum. The researchers on the new study plan to use future Webb data to try to find more black hole seeds.
The research was published in the journal Nature.
Source: University of Cambridge