Using the James Webb Space Telescope (JWST), astronomers have discovered an “extremely red” supermassive black hole growing in the shadowy, early universe.
The red hue of the supermassive black hole, seen as it was around 700 million years after the Big Bang, is the result of the expanding universe. As the universe balloons outward in all directions, light traveling toward us gets “redshifted,” and the redshifted light in this case indicates a cloak of thick gas and dust shrouding the black hole.
Examining JWST data, the astronomy team led by Lukas Furtak and Adi Zitrin of the Ben-Gurion University of the Negev, was also able to determine the mass of the supermassive black hole. At around 40 million times the mass of the sun, it is unexpectedly massive in comparison to the galaxy in which it resides.
The team also found that the supermassive black hole, which is located around 12.9 billion light-years away from Earth, is rapidly feasting on the gas and dust around it. In other words, it’s growing.
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“We were very excited when JWST started sending its first data. We were scanning the data that arrived for the UNCOVER program, and three very compact yet red-blooming objects prominently stood out and caught our eyes,” Furtak said in a statement. “Their ‘red-dot’ appearance immediately led us to suspect that it was a quasar-like object.”
The ‘three red dots’
Quasars are created when copious amounts of matter surround supermassive black holes like this one. This matter forms a disk of gas and dust called an accretion disk that gradually feeds the black hole. The immense gravitational influence of the black hole churns this matter, generating intense temperatures and causing it to glow.
Additionally, matter that doesn’t fall into the supermassive black hole is channeled to the cosmic titan’s poles. Particles in these regions are accelerated to speeds approaching that of light as highly collimated jets. As these relativistic jets are blasted out, the eruptions are accompanied by bright electromagnetic emissions.
As a result of these phenomena, quasars powered by supermassive black holes in active galactic nuclei (AGN) are often so bright that the light they emit often outshines the combined light of every star in the galaxy that surrounds them.
The vast amount of radiation being emitted from around this particular supermassive black hole caused it to take on a small point-like appearance in JWST data.
“Analysis of the object’s colors indicated that it was not a typical star-forming galaxy. This further supported the supermassive blackhole hypothesis,” Rachel Bezanson, from the University of Pittsburgh and co-lead of the UNCOVER program, said in the statement. “Together with its compact size, it became evident this was likely a supermassive black hole, although it was still different from other quasars found at those early times.”
The early quasar wouldn’t have been visible even to the powerful infrared eye of the JWST without a little help from an effect predicted by Albert Einstein in 1915.
Einstein’s lens
Einstein’s theory of general relativity suggests objects of mass warp the very fabric of space and time, which are truly united as a single entity called “spacetime.” The theory continues on that gravity arises as a result of that curvature. The greater the mass of an object, the more “extreme” the curvature of spacetime is.
Not only does this curvature therefore tell planets how to move around stars and stars and how to move around the centers of their home galaxies, but it also changes paths of light coming from those stars.
The closer to the object of mass that light travels, the more its path is “bent.” Different paths of light from a single background object can thus be bent by a foreground, or “lensing object,” and shift the appearance of the background object’s location. Sometimes, the effect can even cause the background object to appear in multiple places in the same image of the sky. Other times, light from the background object is simply amplified, and that object is magnified.
This phenomenon is known as “gravitational lensing.”
In this case, the JWST used a galaxy cluster called Abell 2744 as a foreground lensing body to amplify light from background galaxies, which are otherwise too distant to see. This revealed the extremely red quasar they zeroed-in on, originally in the form of three red dots.
“We used a numerical lensing model that we had constructed for the galaxy cluster to determine that the three red dots had to be multiple images of the same background source, seen when the universe was only some 700 million years old,” Zitrin said.
Further analysis of the background source revealed its light must have come from a compact region.
“All the light of that galaxy must fit within a tiny region the size of a present-day star cluster. The gravitational lensing magnification of the source gave us exquisite limits on the size,” team member and Princeton University researcher Jenny Greene said in the statement. “Even packing all the possible stars into such a small region, the black hole ends up being at least 1% of the total mass of the system.”
The discovery further adds to the mystery of how supermassive black holes, which can be millions (or even billions) of times as massive as the sun, grew to such huge sizes during the universe’s infancy.
“Several other supermassive black holes in the early universe have now been found to show a similar behavior, which leads to some intriguing views of the black hole and host galaxy growth, and the interplay between them, which is not well understood,” Greene said.
The JWST has detected a wealth of “little red dots” over time. These could also indicate feeding supermassive black hole-powered quasars in the early universe, maybe meaning a striking black hole growth conundrum could soon be solved.
“In a way, it’s the astrophysical equivalent of the chicken and egg problem,” Zitrin concluded. “We do not currently know which came first — the galaxy or black hole, how massive the first black holes were, and how they grew.”
The team’s research was published on Feb. 14 in the journal Nature.
