Oldest black hole discovered by the James Webb Space Telescope. Using the James Webb Space Telescope (JWST), a team of astronomers identified the black hole as the most distant ever observed as it consumed its host galaxy. This discovery marks a significant stride in our comprehension of how supermassive black holes attained masses equivalent to millions of billions of times that of the sun during the early epochs of the universe.
Situated in the ancient galaxy GN-z11, this black hole is situated 13.4 billion light years away, providing a glimpse into its state just 400 million years after the Big Bang. The black hole itself weighs approximately 6 million times more than the sun and appears to be devouring matter from its surrounding galaxy at a rate five times faster than current theories suggest is sustainable.
In a statement, Roberto Maiolino, the team leader at the University of Cambridge Department of Physics, characterized the finding as a significant advancement for black hole science, referring to it as "a giant leap forward."
It's very early in the universe to see a black hole this massive, so we've got to consider other ways they might form. Very early galaxies were extremely gas-rich, so they would have been like a buffet for black holes.- Roberto Maiolino
The size of the first supermassive black holes, which appeared when the universe was less than 1 billion years old, poses a problem for formation theories. The conventional expectation is that achieving a mass millions or billions of times that of the sun should require billions of years of continuous feeding, creating a discrepancy in current understanding.
"It's like seeing a family walking down the street, and they have two six-foot teenagers, but they also have with them a six-foot tall toddler," Maynooth University research fellow John Reagan, who was not involved in this research, told reporters. "That's a bit of a problem; how did the toddler get so tall? And it's the same for supermassive black holes in the universe. How did they get so massive so quickly?"
Scientists are currently exploring two primary pathways for the early universe's black holes to attain supermassive status. One route involves the formation of small black hole seeds, originating from the collapse of massive stars after their life cycles. Over millions or billions of years, these seeds gradually accumulate mass. Alternatively, a more direct process could occur, where extensive clouds of cold gas and dust collapse, immediately giving rise to a "heavy black hole seed" with a mass several million times that of the sun.
By bypassing the initial stages, this approach allows the system to fast-forward through millions or billions of years of stellar evolution. This headstart accelerates the feeding and merger processes crucial for the growth of black hole seeds into supermassive black holes. The recent discovery of an ancient black hole with a mass several million times that of the sun lends support to the viability of the heavy seed theory.
However, counter to existing theories, the accelerated rate at which the black hole in GN-z11 is consuming matter suggests the intriguing possibility that black holes might possess the capability to feed at a much swifter pace than observed in other early universe black holes. This finding provides potential support for the small black hole seed theories.
A critical parameter in this context is the Eddington limit, a mathematical formula governing how quickly a celestial body, such as a star, can accumulate mass before the emitted radiation, or luminosity, counteracts gravitational attraction, effectively halting the feeding process.
Despite black holes not emitting light due to their confinement by an event horizon, their substantial gravitational influence causes the surrounding material to undergo intense heating and radiation emission. The luminosity from this region, known as an active galactic nucleus (AGN), intensifies with the black hole's feeding rate. Consequently, the Eddington limit becomes relevant, potentially impeding further material accretion and terminating the black hole's feeding spree.
In the case of the recently discovered black hole, it is ingesting matter from its host galaxy at a rate five times beyond the Eddington limit. While instances of "super-Eddington accretion" can occur intermittently, the team speculates that if this heightened feeding persisted for 100 million years, the black hole might not have needed to originate as a heavy black hole seed. Instead, it could have evolved from a much lighter stellar-mass black hole seed between approximately 250 million and 370 million years after the Big Bang, rapidly attaining its observed mass as captured by the JWST 13.4 million years ago.
An illustration of a rapidly spinning supermassive black hole surrounded by an accretion disc
The team is reasonably confident that the voracious appetite of this black hole is accountable for the existence of GN-z11, a galaxy roughly 100 times smaller than the Milky Way yet exceptionally luminous. However, the insatiable black hole is also likely impeding the development of its host galaxy.
High-speed streams of particles expelled from the vicinity of the feeding black hole are anticipated to displace gas and dust from the core of the galaxy. Since cold clouds of gas and dust play a crucial role in the formation of stars, this suggests that the black hole is effectively halting the birth of stars, consequently hindering the growth of this diminutive galaxy.
Beyond unraveling the mysteries surrounding this black hole and its host galaxy, the research team envisions that the capabilities of the JWST will facilitate the identification of additional black holes in the early universe. Their primary goal is to locate small black hole seeds during the nascent stages of the cosmos, potentially settling the debate surrounding the accelerated growth of supermassive black holes.
It's a new era: The giant leap in sensitivity, especially in the infrared, is like upgrading from Galileo's telescope to a modern telescope overnight. Before the JWST came online, I thought maybe the universe isn't so interesting when you go beyond what we could see with the Hubble Space Telescope. But that hasn't been the case at all: The universe has been quite generous in what it's showing us, and this is just the beginning.- Roberto Maiolino
The team's research was published on Wednesday, Jan. 17, in the journal Nature.