A black hole discovered in Cosmic Dawn is simply too big to easily explain. It is located at the center of a galaxy called J1120+0641 and has a mass of over a billion suns.
There are larger black holes all around us today. The problem is the when of the existence of J1120+0641. Less than 770 million years after the Big Bang, it is difficult to determine how the black hole had time to acquire so much mass.
We’ve known about the galaxy and its overcrowded black hole for more than a decade, and scientists have had ideas about how it formed. Now, observations using the JWST have debunked one of those notions. By all measures, J1120+0641 looks “shockingly normal,” leaving open more exotic explanations for the black hole’s weight gain.
The discovery of J1120+0641 was announced back in 2011 and for a few years it remained the most distant quasar galaxy known. It was actually a good few years. As far as we knew, J1120+0641 was an outlier, with still a possible explanation for its size.
Quasar galaxies are galaxies with a central supermassive black hole that is feeding at an enormous speed. They are surrounded by a huge cloud of gas and dust, which they suck down as fast as they can. The friction and gravity around the black hole heat the material, causing it to shine brightly.
But the speed at which a black hole can feed is not unlimited. The maximum stable speed is determined by the Eddington limit, above which the heated material shines so brightly that the radiation pressure would exceed gravity, pushing the material away and leaving nothing for the black hole to feed on.
Now, black holes can briefly enter super-Eddington accretion, where they exceed this limit and gobble up as much material as possible before the radiation pressure kicks in. This is one possible explanation for the black hole at the center of J1120+ 0641 and, as we find them in greater numbers, other large black holes lurking at the beginning of the universe.
To look for the signs of super-Eddington accretion, astronomers needed data with sufficient resolution to perform a detailed analysis of the galaxy’s light, looking for signatures associated with extreme processes. And for this we needed JWST, the most powerful space telescope ever built, optimized to peer into those far reaches of space and time.
JWST observed the galaxy in early 2023, and a team led by astronomer Sarah Bosman of the Max Planck Institute for Astronomy in Germany parsed the light it collected to catalog the properties of the material surrounding the black hole: a huge torus of dust at the edge and a glowing disk that revolved around the black hole and flowed into it.
This analysis shows that the black hole is actually feeding quite normally. There is nothing about its accretion that is significantly different from other, more recent quasar systems.
One possible explanation for these giant black holes is that extra dust caused astronomers to overestimate their masses. And yet, there is no sign of extra dust.
This means that J1120+0641 is what it appears to be: a fairly normal quasar galaxy, with a black hole that isn’t swallowing up material at a superfast rate. The black hole, and the way it feeds, were already relatively mature when we observed it, within a few hundred million years of the Big Bang.
“Overall, the new observations only add to the mystery: early quasars were shockingly normal,” Bosman says. “No matter what wavelength we observe them in, quasars are virtually identical at all eras of the universe.”
This means that super-Eddington accretion is not the solution to the growth of mysteriously massive black holes at the beginning of time.
The other important explanation is that the black holes initially formed from quite large ‘seeds’. Rather than a slow, gradual process from something the size of a star, this theory posits that the black holes formed by the collapse of clumps of matter or even extremely large stars up to hundreds of thousands of times the mass of the Sun. grow an edge.
Now that we see more and more of these behemoths lurking in the mists of the early universe, this idea seems less bizarre and more like the best possible explanation we have for this mysterious era in the history of our universe.
The research was published in Nature Astronomy.