Astronomers using the NASA/ESA/CSA James Webb Space Telescope have detected a small and vigorous black hole in GN-z11, an exceptionally luminous galaxy that existed just 420 million years after the Big Bang, more than 13 billion years ago. That this black hole with a mass of a few million solar masses even exists so early in the Universe challenges current assumptions about how black holes form and grow.
GN-z11, shown in the inset, is seen as it was 13.4 billion years in the past, just 400 million years after the Big Bang. Image credit: NASA / ESA / P. Oesch, Yale University / G. Brammer, STScI / P. van Dokkum, Yale University / G. Illingworth, University of California, Santa Cruz.
Astronomers believe that the supermassive black holes found at the centre of galaxies like the Milky Way grew to their current size over billions of years.
But the size of this newly-discovered black hole suggests that they might form in other ways: they might be ‘born big’ or they can eat matter at a rate that’s five times higher than had been thought possible.
According to standard models, supermassive black holes form from the remnants of dead stars, which collapse and may form a black hole about a hundred times the mass of the Sun
If it grew in an expected way, this newly-detected black hole would take about a billion years to grow to its observed size.
However, the Universe was not yet a billion years old when this black hole was detected.
“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,” said Dr. Roberto Maiolino, an astronomer at the University of Cambridge.
“Very early galaxies were extremely gas-rich, so they would have been like a buffet for black holes.”
Like all black holes, the young black hole in GN-z11 is accreting material from its host galaxy to fuel its growth.
Yet, this ancient black hole is found to gobble matter much more vigorously than its siblings at later epochs.
GN-z11 is a compact galaxy, about one hundred times smaller than the Milky Way, but the black hole is likely harming its development.
When black holes consume too much gas, it pushes the gas away like an ultra-fast wind.
This ‘wind’ could stop the process of star formation, slowly killing the galaxy, but it will also kill the black hole itself, as it would also cut off the black hole’s source of ‘food.’
“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,” Dr. Maiolino said.
“Before Webb came online, I thought maybe the Universe isn’t so interesting when you go beyond what we could see with the NASA/ESA 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.”
“The sensitivity of Webb means that even older black holes may be found in the coming months and years,” he added.
“We are hoping to use future observations from Webb to try to find smaller ‘seeds’ of black holes, which may help them untangle the different ways that black holes might form: whether they start out large or they grow fast.”
A paper on the findings was published in the journal Nature.
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R. Maiolino et al. A small and vigorous black hole in the early Universe. Nature, published online January 17, 2023; doi: 10.1038/s41586-024-07052-5