An international team of astronomers has discovered the oldest black hole that existed since the cosmic dawn, when the universe was barely 400 million years old, according to a study published on Wednesday.
The detection pushes back the detection of a massive black hole by “about 200 million years,” Jan Scholtz, an astrophysicist at the Kavli Institute of Cosmology at Britain’s University of Cambridge, told AFP.
It will “support a new generation of theoretical models” to explain such a phenomenon in the young universe more than 13 billion years ago, added the co-author of the study published in the journal Nature.
We have to imagine an object with a mass estimated to be 1.6 million times that of our Sun. Invisible, like all black holes, it absorbs surrounding matter by emitting a phenomenal amount of light at its edge.
It was this light that made it possible to reveal the galaxy at its heart, called GN-z11, when its discovery was announced in 2016 using the Hubble Space Telescope.
GN-z11 was then the oldest and therefore the most distant galaxy observed by Hubble. Until the arrival in 2022 of the James Webb Space Telescope, which enabled the detection of the black hole GN-z11.
This detection is added to others made by James Webb that reveal a young universe with objects much brighter than expected.
The black hole discovered by an international team led by Cambridge is dated to 430 million years after the big bang. It is the time of the cosmic dawn, when the first stars and galaxies are born at the end of the so-called “dark” ages.
Several scenarios
The problem for a black hole of this size is understanding how it could have grown so fast. It usually takes several hundred million or several billion years for those discovered later.
Its properties “suggest faster and earlier growth than other black holes known at very early times,” Stéphane Charlot, an astrophysicist at the Paris Institute of Astrophysics and co-author of the study, told AFP.
And therefore “the mechanisms for the formation of black holes in the young universe, which could be different from those we know in the nearby universe”, he adds.
If we stick to classical scenarios, “the universe is then too young to host such a massive black hole, so we have to consider other ways of its appearance,” notes Professor Roberto Maiolino, an astrophysicist from Cambridge and first author of the study, quoted in the press release.
Theorists imagine that such an object was born “large”, from the explosion of a supermassive star at the end of its life, or from the rapid concentration of a cloud of dense gas without going through the star formation stage.
Once the GN-z11 black hole is well born, it would pack into the surrounding gas to grow rapidly. And all the more easily because, according to Mr. Charlot, “observations seem to indicate a high density of this gas.”
Study Nature “doesn’t rule out any of these scenarios,” according to Jan Scholtz, who is relying on the extraordinary observational powers of the James Webb Telescope to shed light on the phenomenon.
“We can expect to detect others when we have a larger number of deep observations of larger parts of the sky,” hopes the astrophysicist.