An object lurking in the misty dawn of the universe has taken astronomers by surprise.
Observations collected by the James Webb Space Telescope have revealed an active supermassive black hole with 9 million times the mass of the sun – one that is actively growing as it gobbles up matter from the space around it.
About 570 million years after the Big Bang, this is the earliest growing supermassive black hole yet detected, though scientists hope it won’t hold the record for long.
The black hole was found in one of the earliest galaxies ever discovered, formerly known as EGSY8p7 and since renamed CEERS 1019. Its discovery could help with one of the biggest puzzles of the early universe: how the black holes in the Cosmic Dawn got so big in such a short time.
In a special edition of The Astrophysical Journal.
“We’ve found the most distant active galactic core (AGN) and the most distant, earliest black hole we’ve ever found,” Larson told ScienceAlert.
Larsson was initial looking at CEERS 1019 as part of her study of light produced by star formation in the very early universe.
This light, called Lyman alpha emission, is believed to be generated by the ionization of neutral hydrogen through star-forming activity. The early universe was filled with a fog of neutral hydrogen, preventing light from propagating; only after this hydrogen was ionized was the light able to flow freely.
This era of reionization, as it is known, is not fully understood. We know it happened in the first billion years after the Big Bang, 13.8 billion years ago, but to see that that far into the early universe is really hard. CEERS 1019 and a handful of other super-early galaxies make excellent targets for this study because they are relatively bright.
The galaxy was identified in Hubble data in 2015and was the earliest, most distant galaxy to be observed at the time.
Subsequent observations confirmed its existence, but more detailed information has remained elusive: the earliest light in the Universe has shifted so far into the infrared part of the spectrum due to the expansion of the Universe that a powerful, dedicated infrared instrument such as JWST is needed to to investigate them.
So when JWST came along, CEERS 1019 – the brightest of the Hubble galaxies from this era – was an obvious target. The telescope only stared at the galaxy for an hour, with all four instruments, but it yielded a wealth of data.
“At the time I was like, wow, look at everything we can see with JWST, we’ve seen this whole part of the spectrum of this galaxy – and all the galaxies early in the universe – that we’ve never seen before seen,” Larson told ScienceAlert.
“I was just overwhelmed by the amount of information.”
But then Larson noticed something she wasn’t quite expecting. In addition to the light from star formation, there was usually a broad emission characteristic associated with AGN. When she told some AGN researchers, things started to get interesting.
Usually, a galaxy in the early universe emits light from an AGN, or light from star formation. It was extremely unexpected to see both in the same galaxy.
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“I was as surprised as anyone,” Larson said.
“We’ve spent weeks discussing which one it should be, it should be one or the other. And it turns out it’s both. There’s some impact that the black hole has on the emission lines that we’re seeing, but most of it light we see in our images is still dominated by the star-forming part of the galaxy.”
That a supermassive black hole existed more than 13.2 billion years agoand was seen growing is not as surprising as you might think.
Much larger black holes have been discovered in the early universe; J1342+0928, a quasar galaxy discovered 690 million years after the Big Bang, has a supermassive black hole clocked at 800 million suns. The black hole inside J0313-1806670 million years after the Big Bang, it was measured on 1.6 billion suns.
Both quasars are dominated by AGN emission. What CEERS 1019 appears to represent, Larson and her colleagues believe, is an intermediate step: a point between the later, larger, AGN-dominated galaxies, and how those galaxies and their black holes began to form in the first place.
“We didn’t and still don’t know how the black holes in those galaxies could get so massive, so early in the Universe,” Larson said.
“So what we found is what we think could be the progenitor or thing that grew into these incredibly massive quasars.”
Looking at the supermassive black hole in CEERS 1019, the researchers think the object was created by the collapse of a massive object, such as one of the first stars in the universe.
These stars were much, much bigger than the stars we have today, so the black hole from such a collapse would have had a head start on its path to becoming supermassive.
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But it would still need a bit of a boost. This could come in the form of periodic super-Eddington accretion. Eddington’s limit is the maximum sustainable rate at which black holes can grow. Material swirls around a black hole in a disk, feeding the black hole like water down a drain.
Above the Eddington limit, the material moves so fast that instead of circling the black hole, it flies off into space. Super-Eddington accretion is only possible for short periods; but according to the team’s modeling, it could possibly be in outbursts that contributed to the growth of the black hole at the center of CEERS 1019.
“We’re not used to seeing so much structure in images at these distances,” says CEERS team member and astronomy Jeyhan Kartaltepe from the Rochester Institute of Technology in New York.
“A galaxy merger could be partly responsible for fueling the activity in this galaxy’s black hole, and that could also lead to more star formation.”
But the best way to learn about it is to find more intermediate galaxies, and this seems extremely feasible.
As Larson points out, the results came from just one hour of observation. The really deep observations are expected to be more distant and reveal even fainter galaxies that will finally help us understand how the Universe came to be and how it grew.
“I don’t think my record will stand for long,” said Larson. “And I hope not, because I think that’s more exciting, that we’re starting to answer these questions.”
The discovery was published in a special edition of The Astrophysical Journal.
An earlier version of this article was published in March 2023.