Supermassive black holes appear to be present at the center of every galaxy, right up to some of the oldest galaxies in the universe. And we have no idea how they got there. It should not be possible for them to grow from supernova remnants to supermassive sizes as quickly as they do. And we’re not aware of any other mechanism that could create something large enough that extreme growth isn’t necessary.
The apparent impossibility of supermassive black holes in the early universe was already a bit of a problem; the James Webb Space Telescope only made it worse by finding even earlier cases of galaxies with supermassive black holes. In the latest example, researchers used Webb to characterize a quasar powered by a supermassive black hole as it existed approximately 750 million years after the Big Bang. And it looks surprisingly normal.
Looking back in time
Quasars are the brightest objects in the universe, powered by the active power of supermassive black holes. The galaxy that surrounds them supplies them with enough material that they form bright accretion disks and powerful jets, both of which emit large amounts of radiation. They are often partially shrouded in dust, which glows by absorbing some of the energy emitted by the black hole. These quasars emit so much radiation that they eventually expel some of the nearby material from the galaxy entirely.
Thus, the presence of these elements in the early universe would tell us that supermassive black holes were not only present in the early universe, but were also integrated into galaxies, as they are in more recent times. But it was very difficult to study them. We didn’t identify many to begin with; there are only nine quasars that date back to when the universe was 800 million years old. This distance makes it difficult to distinguish features, and the redshift caused by the expansion of the universe takes intense UV radiation from many elements and stretches them deep into the infrared.
However, the Webb Telescope was designed specifically to detect objects in the early universe by being sensitive to the infrared wavelengths where this radiation manifests. So the new research is based on pointing Webb at the first of the first nine quasars to be discovered, J1120+0641.
And it looks… remarkably normal. Or at least much like quasars from more recent periods of the universe’s history.
Mostly normal
The researchers analyze the continuum of radiation produced by the quasar and find clear indications that it is embedded in hot, dusty material, as seen in later quasars. This dust is slightly hotter than in some of the newer quasars, but this appears to be a common feature of these objects in the earlier stages of the universe’s history. Radiation from the accretion disk is also visible in the emission spectrum.
Different ways of estimating mass-produced black hole values ​​in region 109 times the mass of the Sun, clearly placing it in the region of supermassive black holes. There is also evidence, from a slight blue shift in some of the radiation, that the quasar is blasting material at about 350 kilometers per second.
There are a few quirks. One is that the material also appears to be falling in at about 300 kilometers per second. This could be caused by the rotation of material in the accretion disk away from us. But if it does, the material rotating towards us on the opposite side of the disk should match. This has been observed several times in very early quasars, but the researchers admit that “the physical origin of this effect is unknown.”
One possibility they suggest as an explanation is that the entire quasar is moving, torn from its position at the center of the galaxy by an earlier merger with another supermassive black hole.
Another peculiarity is that there is also a very rapid outflow of highly ionized carbon – it moves at about twice the speed of quasars at later times. This has been seen before, but there is no explanation for that either.
How did it happen?
Despite the peculiarities, this object looks a lot like recent quasars: “Our observations show that the complex structures of the dust torus and [accretion disk] they can settle around a [supermassive black hole] less than 760 Myr after the Big Bang.”
And again, this is a bit of a problem because it suggests the presence of a supermassive black hole integrated into its host galaxy very early in the history of the universe. To reach the size we see here, black holes push against what’s called the Eddington limit—the amount of material they can absorb before the resulting radiation pushes out neighboring material and chokes the black hole’s food supply.
This suggests two possibilities. One is that these things have been consuming material well beyond the Eddington limit for most of their history—something we haven’t observed, and something that certainly isn’t true of this quasar. Another possibility is that they started massively (around 104 times the mass of the Sun) and the feeding continued at a more reasonable rate. But we really don’t know how something so big could come into existence.
So the early universe remains a pretty confusing place.
Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02273-0 (About DOI).