The black hole discovered lurking at the cosmic dawn is too large to be easily explained. This galaxy is located at the center of a galaxy called J1120+0641, which has a mass of more than a billion suns.
There are bigger black holes all around us today. The problem is when Because there is J1120+0641. Less than 770 million years after the Big Bang, it’s hard to know how the black hole had enough time to gain so much mass.
We’ve known about the galaxy and its massive black hole for more than a decade, and scientists have had ideas about how it came to be. Now, observations using James Webb Scientists have rejected one of these concepts. By all accounts, J1120+0641 appears “shockingly normal,” leaving the door open to more exotic explanations for the black hole’s increased weight.
J1120+0641 detected Announced back in 2011For a few years it remained the most distant known quasar galaxy. It was a good few years, actually. As far as we knew, J1120+0641 was an oddball, and there was only one possible explanation for its size left on the table.
Quasars are galaxies that contain a supermassive central black hole that is feeding at a tremendous rate. They are surrounded by a huge cloud of gas and dust, which is sucking them in as fast as it can. The friction and gravity around the black hole heats up the material, making it shine brightly.
But the speed at which a black hole can feed is not unlimited. The maximum stable rate is determined by Eddington limitafter which the hot material shines so intensely that… The radiation pressure will exceed the force of gravity.pushing matter away and leaving nothing for the black hole to feed on.
Now, black holes can briefly enter Eddington superaccretion, pushing themselves through that limit and swallowing as much matter as possible before the radiation pressure kicks in. This is one possible explanation for the black hole at the center of J1120+0641, and since we are finding them in larger numbers, there are other large black holes lurking in the early universe.
In order to search for signs of Eddington superaccretion, astronomers needed data of sufficient resolution to perform a detailed analysis of the galaxy’s light, looking for signs associated with extreme processes. That’s why we needed the James Webb Space Telescope, the most powerful space telescope ever built, optimized for looking at those far reaches of space and time.
The James Webb Space Telescope observed the galaxy in early 2023, and a team led by astronomer Sarah Bosman of the Max Planck Institute for Astronomy in Germany deconstructed the light it collected to catalog the properties of the material surrounding the black hole: a massive torus of dust on the galaxy’s outskirts, and a glowing disk swirling around it that feeds into the black hole.
This analysis reveals that the black hole is feeding very normally, and nothing about its accretion looks significantly different from other, more recent quasar galaxies.
One possible explanation for these giant black holes is that excess dust was causing astronomers to overestimate their masses. However, there is no indication of additional dust either.
This means that J1120+0641 is what it looks like: a fairly ordinary quasar galaxy, with a black hole that is not gobbling up material at very high rates. The black hole, and the way it feeds, was relatively mature by the time 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.” Boseman says“No matter what wavelengths we observe them at, quasars are almost identical throughout all ages of the universe.”
This means that Eddington superaccretion is not the answer to the growth of the puzzlingly massive black holes at the dawn of history.
Another leading explanation is that black holes initially formed from very large “seeds.” Rather than a slow, gradual process from something the size of a star, this theory suggests that black holes formed from the collapse of clumps of matter or even very massive stars with masses hundreds of thousands of times the mass of the Sun, giving their growth a head start.
As we find more and more of these giant monsters lurking in the fog of the early universe, this idea seems less outlandish, and more like the best possible explanation we have for this mysterious era in our universe’s history.
The research was published in Nature astronomy.
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