Using the James Webb Space Telescope (JWST), astronomers have spotted a supermassive black hole at the “cosmic dawn” that appears incredibly massive. The confusion comes from the fact that this giant void doesn’t appear to have been feasting on surrounding matter during this period – but, to reach its immense size, one would expect it to have been voracious at the beginning of time.
The supermassive black hole powering a quasar at the heart of galaxy J1120+0641 was observed as it was when the Universe was only about 5% of its current age. It also has a mass more than a billion times that of the Sun.
While it is relatively easy to explain how closer, and therefore newer, supermassive black holes grew to billions of solar masses, the merging and feeding processes that facilitate such growth should take about a billion years. This means that finding such supermassive black holes existing before the 13.8 billion-year-old universe is a billion years old is a real dilemma.
Since it began operations in the summer of 2022, JWST has proven particularly effective at spotting these hard-to-detect black holes at cosmic dawn.
One theory surrounding the early growth of these voids is that they were engaged in a feeding frenzy called an “ultra-efficient feeding pattern.” However, observations of the supermassive black hole J1120+0641 by JWST showed no particularly effective feeding mechanisms in the material in its immediate vicinity. The discovery casts doubt on the growth mechanism of ultrafast-feeding supermassive black holes and means scientists may know even less about the early evolution of the cosmos than they thought.
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“Overall, the new observations only add to the mystery: The first quasars were incredibly normal,” Sarah Bosman, team leader and postdoctoral researcher at the Max Planck Institute for Astronomy (MPIA), said in a statement. “Regardless of the wavelengths in which we observe them, quasars are nearly identical at all times in the universe.”
Supermassive black holes control their own power
Over the 13.8 billion years of cosmic history, galaxies have grown by gaining mass, either by absorbing surrounding gas and dust, by cannibalizing smaller galaxies, or by merging with larger galaxies.
About 20 years ago, before JWST and other telescopes began discovering puzzling supermassive black holes in the early universe, astronomers thought that supermassive black holes at the heart of galaxies gradually expanded along with the processes that drove galactic growth.
In fact, there are limits to how fast a black hole can grow — limits that these cosmic titans themselves helped set.
Due to the 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. Additionally, the immense gravity of the central black hole gives rise to powerful 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 eclipse the combined light of all the stars in the surrounding galaxy. The regions where all this happens are called quasars, and they represent some of the brightest celestial objects.
This luminosity also has another function. Although it has no mass, light exerts pressure. This means that the light emitted by quasars pushes on the surrounding matter. The faster the black hole feeding the quasar feeds, the higher the radiation pressure and the more likely the black hole will cut off its own supply and stop growing. The point at which black holes, or any other accretor, starve themselves by pushing away the surrounding matter is known as the “Eddington limit.”
This means that supermassive black holes cannot feed and grow as fast as they would like. So finding supermassive black holes with masses as large as 10 billion suns in the early cosmos, especially less than a billion years after the Big Bang, is a real problem.
Astronomers need to know more about the first quasars to determine whether the first supermassive black holes could have exceeded the Eddington limit and become “super-Eddington accretors.”
To do this, in January 2023, the team focused the JWST Mid-Infrared Instrument (MIRI) on the quasar at the heart of J1120+0641, located 13 billion light years away and observed as it was only 770 million years after the Big Bang. This study constitutes the first mid-infrared study of a quasar that existed at the cosmic dawn.
The light spectrum of this primitive supermassive black hole revealed the properties of the large ring-shaped “torus” of gas and dust that surrounds the accretion disk. This torus helps guide matter toward the accretion disk, from where it is gradually funneled toward the supermassive black hole.
MIRI observations of this quasar have shown that the cosmic supply chain functions similarly to that of “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 improved power mechanism led to the rapid growth of the first black holes.
Additionally, measurements of the region around the supermassive black hole, where matter swirls at near the speed of light, agree with observations of the same regions of modern quasars.
JWST observations of this quasar revealed a major difference between it and its modern counterparts. The dust in the torus surrounding the accretion disk had a temperature of about 1,130 degrees Celsius, about 100 degrees warmer than the dust rings surrounding quasars powered by supermassive black holes observed closer to Earth.
The research favors another method of early growth of supermassive black holes that suggests these cosmic titans had a head start in the early universe, forming from already massive black hole “seeds.” These heavy seeds would have had masses at least a hundred thousand times greater than the Sun, forming directly via the collapse of early, massive gas clouds.
The team’s research was published June 17 in the journal Nature Astronomy.
Originally published on Space.com.