Astronomers have discovered the oldest black hole ever observed, dating back more than 13 billion years to the origins of the universe.
Observations with the James Webb Space Telescope (JWST) show that it is at the heart of a galaxy 440 million years after the Big Bang. At about a million times the mass of the Sun, it is surprisingly large for a baby black hole, raising the question of how it got so big so quickly.
Professor Roberto Maiolino, an astrophysicist at the University of Cambridge who led the observations, said: “The surprise is that it is so huge. That was the most unexpected thing.”
The observations, published on the preprint website Arxiv, do not form a direct image, which is invisible because no light can escape its grasp. But astronomers discovered telltale features of the accretion disk, the halo of gas and dust that quickly swirls around the cosmic sinkhole.
Astronomers believe the earliest black holes could help unravel a puzzle about how their giant counterparts at the centers of galaxies like the Milky Way grew to be billions of times the mass of the Sun. Until recently, it was thought that they had simply snowballed over nearly 14 billion years, growing steadily through mergers and by gobbling up stars and other objects. But this snowball scenario cannot fully explain the epic proportions of today’s supermassive black holes.
The latest observations, from the galaxy called GN-z11, bring the origins of this mystery back to the infancy of black holes and suggest that they were either born large or grew extremely quickly early on.
“Understanding where black holes came from in the first place has always been a puzzle, but now that puzzle appears to be deepening,” said Prof. Andrew Pontzen, a cosmologist at University College London, who was not involved in the study. “These results, using the power of JWST to look back in time, suggest that some black holes in the early universe grew very quickly, much faster than we expected.”
One explanation, known as the heavy seed scenario, is that an early generation of black holes formed from the direct collapse of massive gas clouds, rather than from burned-out stars that collapsed under their own gravity at the end of their lives. Another possibility is that compact clusters of stars and black holes merged very quickly in the early universe.
A third, more speculative hypothesis is the existence of so-called primordial black holes that formed during the cosmic inflation, the period of faster-than-light expanding universe that occurred a fraction of a second after the Big Bang.
This would turn the supposed play order on its head, where galaxies came first and then black holes started growing into them. Primordial black holes are said to have been effectively woven into the fabric of the cosmos from the beginning.
“If that were true, it would have major consequences for the opening fraction of a second of our universe,” Pontzen said. “Regardless, the story of how black holes and galaxies grew up together is a compelling one that we are only just beginning to piece together.”
The findings are the latest in a series of stunning discoveries by NASA’s space observatory, just two years after launch. JWST is about 100 times more sensitive than previous telescopes, such as Hubble, at detecting infrared light, the part of the spectrum used to see the most distant objects. “It essentially amounts to upgrading Galileo’s telescope into a modern telescope. It is 400 years of discoveries potentially compressed into the time span of JWST operations,” Maiolino said.
He said that before the telescope’s launch, there was a possibility that it would open a new window on “a boring extension of what we know.” “That’s not what we’re seeing,” Maiolino said. “The universe has been quite generous. We really discover things that we didn’t expect.”
What is a black hole?
Black holes are among the weirdest and most ominous objects in the universe. They have such intense gravity that neither matter nor light can escape their grasp. The threshold of a black hole is demarcated by the event horizon, the point of no return. Anything that crosses this line is gone forever.
They are challenging to study because they are fundamentally invisible, but applying the laws of physics yields some bizarre insights. When approaching a black hole, the gravitational gradient can be so extreme that objects become stretched out in a process known as spaghettification. At the event horizon, gravity is so intense that light is bent in a perfect loop around the black hole, meaning that if you stood there you could see the back of your own head.
What lies beyond the event horizon is unknown. Einstein’s general theory of relativity suggests that the density at the center of a black hole would become infinite, creating a gravitational singularity. This break in space-time would have no ‘where’ or ‘when’ and would be beyond the reach of conventional laws of nature. But it is not clear whether such singularities actually exist.
Black holes come in different sizes. Stellar black holes, formed from the remains of massive stars, can be up to twenty times heavier than our Sun. Supermassive black holes, such as Sagittarius A* at the center of the Milky Way, can have a mass equivalent to millions or billions of suns and play a crucial role in galactic evolution.
Astronomers have made significant progress in observing black holes over the past decade, with the first image of a human halo captured by the Event Horizon telescope in 2019, and observations of cataclysmic black hole mergers through the detection of gravitational waves traveling through space time rippled. . The latest observations and even more distant James Webb targets will help determine the origins of these mysterious objects.