Using the James Webb Space Telescope (JWST), astronomers have spotted a supermassive black hole in a “cosmic dawn” that looks incredibly massive. The confusion comes from the fact that this giant void doesn’t appear to have fed on much surrounding matter during this time – but to reach its massive size, one would expect it to have been voracious at the beginning of time.
The feeding supermassive black hole that powers a quasar at the heart of galaxy J1120+0641 was seen as it was when the universe was only about 5% of its current age. It also has a mass that is over a billion times that of the sun.
Although it is relatively easy to explain how closer, and therefore more recent, supermassive black holes have grown to billions of solar masses, the merger and refueling processes that facilitate such growth are expected to take about a billion years. This means that discovering such supermassive black holes that existed before the 13.8 billion year old universe was 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 challenging black holes in the cosmic dawn.
One theory surrounding the early growth of these cavities is that they were engaged in a nutritional frenzy called “ultra-efficient feeding.” However, JWST observations of the supermassive black hole in J1120+0641 do not indicate a particularly efficient mechanism for supplying material in its immediate vicinity. This discovery casts doubt on the superfast growth mechanism of the supermassive black hole and means that 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 early quasars were shockingly normal,” team leader and Max Planck Institute for Astronomy (MPIA) postdoctoral fellow Sarah Bosman said in a statement. “No matter what wavelengths we observe them at, quasars are nearly identical across 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 in size by gaining mass or by absorbing the 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 had hypothesized that supermassive black holes at the hearts of galaxies grew gradually in step with the processes that 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 themselves.
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. In addition, the massive gravity of the central black hole generates powerful tidal forces that create turbulent conditions in the accretion disk, heating it and causing it to emit light in the electromagnetic spectrum. These emissions are so bright that they often outshine the combined light of every star in the surrounding galaxy. The regions where all this happens are called quasars and are some of the brightest objects in the sky.
This brightness has another function. Although it has no mass, light exerts pressure. This means that the light emitted by the quasars pushes on the surrounding matter. The faster the black hole feeding the quasar, 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 out the surrounding matter is known as the “Eddington limit”.
This means that supermassive black holes can’t just feed and grow as fast as they want. Thus, the discovery of supermassive black holes with the mass of 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 early quasars to determine whether early supermassive black holes were able to overcome the Eddington limit and become so-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 seen just 770 million years after the Big Bang. The investigation represents the first mid-infrared study of a quasar that existed at the dawn of space.
The spectrum of light from this early supermassive black hole reveals the properties of the large, ring-shaped “torus” of gas and dust that surrounds the accretion disk. This torus helps guide matter into the accretion disk, from where it is gradually fed into the supermassive black hole.
MIRI observations of this quasar showed that the cosmic supply chain functions similarly to that of “modern” quasars closer to Earth, which therefore exist in the later ages of the universe. This is bad news for proponents of the theory that an improved feeding mechanism led to the rapid growth of early black holes.
Furthermore, measurements of the region around the supermassive black hole, where matter rotates at nearly the speed of light, are consistent with observations of the same regions of modern quasars.
JWST observations of this quasar revealed one major difference between it and its modern counterparts. The dust in the dust surrounding the accretion disk had a temperature of about 2,060 degrees Fahrenheit (1,130 degrees Celsius), which is about 100 degrees hotter than the dust rings around supermassive black hole-powered quasars observed closer to Earth.
The research supports another method of early supermassive black hole growth, which suggests that these cosmic titans had a head start in the early universe, forming from black hole “seeds” that were already massive. These heavy seeds would have a mass at least a hundred thousand times that. of the sun, forming directly through the collapse of early and massive gas clouds.
The team’s research was published June 17 in the journal Nature Astronomy.
Originally published on Space.com.
