Hubble Space Telescope finds elusive black hole in star cluster : NPR

Using the Hubble Space Telescope, astronomers have found evidence of an elusive black hole with a mass about 8,000 times that of the sun.

What makes this black hole special is its size. report About Discover Journals Nature.

That’s much bigger than typical black holes formed when dead stars collapse, but not as big as the supermassive black holes that lurk at the centers of galaxies and can house hundreds of thousands or even millions of suns.

Scientists have long searched for intermediate black holes like this new one, because their discovery could shed light on the different ways black holes form and why they grow into gigantic monsters.

But despite many years of intense effort, scientists haven’t had much luck finding a solid example of a black hole in the so-called intermediate size range, which includes black holes between 100 and 100,000 times the mass of the Sun.

“So people wonder if they’re hard to find because they’re not there, or if they’re hard to detect,” he says. Maximilian Heberle of the Max Planck Institute for Astronomy in Heidelberg, Germany.

He and a few colleagues recently decided to search for it in a large, bright star cluster known as Omega Centauri, a dense, spherical cloud of millions of stars located about 17,000 light-years from Earth.

Black holes cannot be observed directly because their gravity attracts everything, including light, but researchers can study whether their gravity affects nearby objects, including stars.

And the researchers knew that the stars in this particular cluster are continually observed by the Hubble Space Telescope, which takes images of the cluster’s central region every year.

“This is actually for technical reasons, to calibrate the equipment,” Hebel says.

The telescope had been providing high-quality observations going back more than 20 years, allowing Hebel and his colleagues to precisely measure the motions of the cluster’s 1.4 million stars.

“The list of stars whose motion we have measured is much longer than any previous study,” he said, adding that the stars are all “moving in random directions, like a swarm of insects.”

In the end, the researchers were able to find seven stars in the center that are moving much faster than the other stars — so fast in fact that they should be flying out of the cluster and gone forever.

The fact that the black hole is stuck in the center and concentrated there means “there must be something gravitationally pulling on it to stop it escaping,” Hebel said. And the only object that could be this massive is an intermediate-mass black hole, which has a mass at least 8,000 times that of the sun.

He says it’s unlikely that the black hole will become more massive than about 50,000 times the mass of the sun, because if it did, scientists would expect many more stars to be affected by its gravity.

He had previously Claim The idea that a potential medium-sized black hole could be found in the cluster dates back to 2008, but has been disputed.

This time, with the additional years of data “I think our evidence is much stronger,” he says.

Additionally, future observations are already planned by the James Webb Space Telescope, a powerful telescope that will be able to look for signs of gas being heated as it falls into the black hole.

“This is really exciting, right? This is the second black hole where we can see individual stars flying around it.” Jenny GreenAstrophysicist at Princeton University.

She said the only other similar observation was a Nobel Prize-winning study that observed stars whizzing around a black hole at the center of the Milky Way, a supermassive galaxy with a mass about four million times that of the sun.

“So I think this is a really big event, and it’s a much smaller mass black hole,” she says.

No one knows how black holes of this size form.

One possibility is that smaller black holes may merge into larger ones. detection The gravitational waves generated by the collision of two black holes created a black hole with a mass about 150 times that of the Sun.

Another way to grow medium-sized black holes has recently been proposed. was suggested Astronomers hypothesize that in dense star clusters like Omega Centauri, many stars collide to form a single, very massive star, which then collapses into a medium-sized black hole.

Understanding where intermediate black holes are and how they grow can help scientists understand what role they play in the evolution of even more massive black holes at the centers of galaxies.

“The newly discovered black hole could tell us important information about how these massive black holes first formed and grew,” Green said.

Such supermassive black holes appear to have emerged remarkably early since the beginning of the universe, just a few hundred million years after the Big Bang.

it is New Observations The image, taken by the James Webb Space Telescope, has astronomers puzzled as to how a black hole could grow so large so quickly.

Before these observations, Green said, he thought galaxies grew first, and then black holes formed at their centers. “I’m not so sure now,” he said. “We have some intriguing evidence that black holes grew faster than galaxies.”

Green said that the intermediate-sized black holes that exist today could be relics left over from earlier black-hole formation processes, and could provide clues about how they came about.

“You need more than one thing to get the full picture at the end of the day,” she said, “but this is a real door opener.”