Using the James Webb Space Telescope (JWST), astronomers have spotted a supermassive black hole at “cosmic dawn” that appears incredibly massive. The confusion arises from the fact that it does not appear that this giant void was 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 that powers a quasar at the heart of the galaxy J1120+0641 was observed as it was when the universe was only about 5% of its current age. Its mass is also a billion times greater than 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 such difficult-to-detect black holes at the 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.
Related: How did supermassive black holes get so big so quickly right after the Big Bang?
“Overall, the new observations only add to the mystery: the first quasars were incredibly normal,” said Sarah Bosman, team leader and postdoctoral researcher at the Max Planck Institute for Astronomy (MPIA), in a press release. “Whatever wavelengths we observe them in, quasars are almost 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. large.
About 20 years ago, before JWST and other telescopes began discovering troubling supermassive black holes in the early universe, astronomers thought that supermassive black holes at the hearts of galaxies gradually grew as processes which led to galactic growth.
In fact, there are limits to how fast a black hole can grow – limits that these cosmic titans actually help 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 represent some of the brightest celestial objects.
This brightness also has another function. Even though it has no mass, light exerts pressure. This means that the light emitted by quasars pushes 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 food supply and stop growing. The point at which black holes, or any other accretors, starve by pushing out surrounding matter is known as the “Eddington limit.”
This means that supermassive black holes cannot simply feed and grow as fast as they want. So finding supermassive black holes with masses of up to 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 were able to exceed the Eddington limit and become what are called “super-Eddington accretors.”
To do this, in January 2023, the team focused JWST’s 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 Great Slam. The survey constitutes the first mid-infrared study of a quasar that existed at the cosmic dawn.
The spectrum of light from this first 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 almost the speed of light, were consistent 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 around the accretion disk had a temperature of about 2,060 degrees Fahrenheit (1,130 degrees Celsius), about 100 degrees warmer than the dust rings around supermassive quasars propelled by black holes observed more near the 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.