Using the James Webb Space Telescope (JWST), astronomers have spotted a supermassive black hole behind the “cosmic dawn” that appears to be impossibly massive. The confusion comes from the fact that this giant void doesn’t seem to have feasted on much of the surrounding matter during that time—but to reach its immense size, one would expect it to have been hungry at the beginning of time.
The feeding supermassive black hole that powers the quasar at the heart of galaxy J1120+0641 has been seen as it was when the universe was only about 5% of its current age. It also has a mass that is more than a billion times that of the Sun.
While it is relatively easy to explain how closer, and thus newer, supermassive black holes grew to billions of solar masses, the merger and power processes that facilitate such growth are expected to take something like a billion years. This means that finding such supermassive black holes that existed before the 13.8-billion-year-old universe was a billion years old is a real dilemma.
Since its launch in the summer of 2022, JWST has proven particularly effective at observing such challenging black holes in the cosmic dawn.
One theory surrounding the early growth of these cavities is that they were involved in a feeding frenzy called an “ultra-efficient feeding regime.” However, JWST’s observations of the supermassive black hole in J1120+0641 have not shown any particularly efficient feeding mechanism in the material in its immediate vicinity. The finding casts doubt on the ultrafast growth mechanism of a supermassive black hole and means scientists may know even less about the early evolution of the universe than they realized.
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“Overall, these new observations only add to the mystery: early quasars were shockingly normal,” team leader and Max Planck Institute for Astronomy (MPIA) postdoctoral researcher Sarah Bosman said in a statement. “Regardless of what wavelengths we observe them at, quasars are almost identical at all epochs of the universe.”
Supermassive black holes control their own diet
Over the past 13.8 billion years of cosmic history, galaxies have grown larger by acquiring mass either by ingesting surrounding gas and dust, by cannibalizing smaller galaxies, or by merging with larger galaxies.
About 20 years ago, before JWST and other telescopes began finding disturbing supermassive black holes in the early universe, astronomers assumed that supermassive black holes in the hearts of galaxies grew gradually in accordance with the processes that led to galactic growth.
In fact, there are limits to how fast a black hole can grow—limits that these space titans actually help set.
Due to conservation of angular momentum, matter cannot fall directly into a black hole. Instead, a flattened cloud of matter called an accretion disk forms around the black hole. In addition, the immense gravity of the central black hole produces strong tidal forces that create turbulent conditions in the accretion disk, heating it and causing it to emit light across the electromagnetic spectrum. These emissions are so bright that they often exceed the combined light of every star in the surrounding galaxy. The regions where all this happens are called quasars, and they represent some of the brightest objects in the sky.
This brightness also has another function. Although light has no mass, it exerts pressure. This means that the light emitted by quasars pushes on the surrounding matter. The faster the black hole feeding the quasar is fueled, the greater the radiation pressure, and the more likely the black hole will cut off its own food supply and stop growing. The point at which black holes or any other accretor starves by pushing away the surrounding matter is known as the “Eddington limit”.
This means that supermassive black holes can’t just feed themselves and grow as fast as they want. So finding supermassive black holes with the mass of up to 10 billion suns in the early universe, especially less than a billion years after the Big Bang, is a real challenge.
Astronomers need to know more about early quasars to determine whether early supermassive black holes were able to break the Eddington limit and become so-called “super-Eddington accretors.”
To that end, in January 2023, the JWST Mid-Infrared Instrument (MIRI) team focused on the quasar at the heart of J1120+0641, located 13 billion light-years away and seen as if it were only 770 million years after the Big Bang. The research represents the first mid-infrared study of a quasar that existed in the cosmic dawn.
The spectrum of light from this early supermassive black hole revealed the properties of a large annular “torus” of gas and dust that circles the accretion disk. This torus helps guide matter to the accretion disk, from where it is gradually fed into the supermassive black hole.
MIRI observations of this quasar have shown that the cosmic supply chain operates similarly to “modern” quasars closer to Earth, which therefore exist in later epochs of the universe. This is bad news for proponents of the theory that an enhanced feeding mechanism led to the rapid growth of early black holes.
Moreover, measurements of the region around the supermassive black hole, where matter swirls at nearly the speed of light, matched observations of the same regions of modern quasars.
JWST’s observations of this quasar revealed one major difference between it and its modern counterparts. The dust in the torus around the accretion disk was around 2,060 degrees Fahrenheit (1,130 degrees Celsius), about 100 degrees hotter than the dust rings around supermassive black hole-powered quasars seen closer to Earth.
The research favors a different method for the early growth of supermassive black holes, suggesting that these cosmic titans got a head start in the early universe when they formed from “seeds” of black holes that were already massive. These heavy seeds would have masses at least a hundred thousand times greater. Suns that form directly from the collapse of early and massive clouds of gas.
The team’s research was published June 17 in the journal Nature Astronomy.
Originally published on Space.com.