Astronomers have discovered a monster black hole lurking in the distant reaches of the Universe1. It gives scientists the best look yet at a black hole that formed very early in cosmic history and shows how these gravitational abysses took shape and grew.
The discovery “provides a wealth of new information on how the seeds of today’s supermassive black holes came about”, says Ákos Bogdán, an astrophysicist at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. He led the work, published on 6 November in Nature Astronomy.
The newfound black hole dwells in a galaxy called UHZ1. To an observer on Earth, UHZ1 lies behind a cluster of other galaxies. The gravity of those intervening objects brightens the light from more distant ones, including UHZ1, which is seen as it was just 470 million years after the Big Bang.
Other astronomers used the James Webb Space Telescope (JWST) to photograph UHZ1 in infrared light. Bogdán and his colleagues then used the orbiting Chandra X-ray Observatory to study it in X-rays, which are emitted by gas being sucked into black holes.
Giant among giants
On the basis of the brightness and other features of the X-rays coming from UHZ1, the scientists calculated that it hosts a black hole — a giant with a mass of between 10% and 100% of the combined mass of the galaxy’s stars. That’s enormous compared with black holes closer to Earth; the black hole at the centre of the Milky Way has about 0.1% of the mass of the Galaxy’s stars.
“It’s really awesome to see a massive black hole so early on,” says Daryl Haggard, an astrophysicist at McGill University in Montreal, Canada.
Some astronomers favour a theory that early black holes grew from ‘light’ — relatively low-mass — seeds produced when the Universe’s first stars exploded. But UHZ1’s age contradicts that: 470 million years isn’t enough time for the Universe to be born, for stars to form and die, and for black holes to grow.
The finding supports an alternate idea — that early black holes were born from ‘heavy’ seeds formed as gas clouds collapsed. “We think this is pretty compelling evidence for heavy seeding,” says study co-author Priyamvada Natarajan, an astrophysicist at Yale University in New Haven, Connecticut.