Evidence of theorized type of black hole discovered near dawn of time
Astronomers have discovered evidence of a theorized type of black hole lurking in the distant universe. Known as an “Outsize Black Hole,” this object could help explain some fundamental cosmic mysteries, including how supermassive monsters form.
Black holes as we know them tend to fall into two categories: there’s the stellar mass black holes, which as the name suggests have masses equivalent to a few stars. They form when large stars die in a supernova. Up the other end of the scale sits supermassive black holes, which contain the mass of millions or even billions of stars. These are found at the center of many galaxies, including our own.
It was long thought that supermassive black holes form by growing out of stellar mass black holes as they slurp up matter over billions of years. This hypothesis was seemingly bolstered by recent observations of intermediate mass black holes, rare objects that slot in the middle of the mass range.
But as astronomers peer farther away in space and time, they’ve increasingly spotted signs that the story isn’t that simple. In 2017, a black hole with a mass of 800 million Suns was discovered in a distant corner of space that meant it grew that big just a few hundred million years after the Big Bang – a growth rate that should be impossible according to our models. And it’s far from alone, with over 100 contemporary giants found since then.
One possible explanation is that some black holes may form through other methods, giving them a larger starting mass than a regular old supernova would allow. If massive clouds of gas collapse, the hypothesis goes, they could form black holes with masses between about 10,000 and 100,000 Suns.
“There are physical limits on how quickly black holes can grow once they’ve formed, but ones that are born more massive have a head start,” said Andy Goulding, co-author of the study. “It’s like planting a sapling, which takes less time to grow into a full-size tree than if you started with only a seed.”
Now astronomers claim to have discovered the first evidence for just such an object, which they call an Outsize Black Hole. It’s located in a galaxy called UHZ1, at the incredible distance of 13.2 billion light-years from Earth – which also means we’re seeing it as it was 13.2 billion years ago, or less than 500 million years after the Big Bang.
Finding the object so far away required the combined power of the Chandra X-ray Observatory and the James Webb Space Telescope, aided by a magnification effect called gravitational lensing. A foreground galaxy cluster magnified the faint light from UHZ1, allowing the two telescopes to pick it up.
From the brightness and energy of the X-rays thrown off by the black hole, the astronomers estimated that its mass is between 10 million and 100 million Suns. That means it has about the same mass as all the stars in its home galaxy put together, which is a far higher percentage than supermassive black holes found in more modern galaxies. These observed characteristics agree with the theoretical predictions of Outsize Black Holes.
“We think that this is the first detection of an ‘Outsize Black Hole’ and the best evidence yet obtained that some black holes form from massive clouds of gas,” said Priyamvada Natarajan, co-author of the study. “For the first time we are seeing a brief stage where a supermassive black hole weighs about as much as the stars in its galaxy, before it falls behind.”
Other studies have suggested that these early giants could have formed from primordial supermassive stars going supernova, or even the collapse of self-interacting dark matter. Of course, it’s possible that there are multiple mechanisms at play, but only further observations can help astronomers pin down the answer.