For the last two years, the James Webb Space Telescope has imaged galaxies that are further away than any seen before, revealing the Universe as it was when it was only a billion years old.
But it has also revealed a problem: the black holes at the centre of these galaxies are already far larger than they should be, given the time they’ve had to grow.
A new study suggests that the key could lie with dark matter.
More about black holes
A team from the University of California, Los Angeles (UCLA) looked into the theory that supermassive black holes form directly from the collapse of giant gas clouds, rather than going through the intermediate step of forming stars first.
For this to happen, the gas needs to stay together as one giant cloud. Under normal conditions, the clouds cool too quickly, causing them to fragment.
"How quickly the gas cools has a lot to do with the amount of molecular hydrogen," says Yifan Lu, who led the study.
"Hydrogen clouds in the early Universe had too much molecular hydrogen, and the gas cooled quickly and formed small halos instead of large clouds."
To prevent this from happening, Lu suggests some form of radiation could break apart the molecular hydrogen, so the clouds are slower to cool.
One potential source of radiation is from an unlikely candidate – dark matter.
No one knows exactly what dark matter is, but theories predict it may have been unstable in the early Universe, releasing a photon when it decays.
The study found that even if only a small fraction of dark matter decayed, the photons produced would disrupt enough of the hydrogen to allow the black holes to grow.
"If these supermassive black holes formed by the collapse of a gas cloud, maybe the additional radiation required would have to come from the unknown physics of the dark sector," says Zachary Picker, also from UCLA.
