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HomescienceHubble Space Telescope Discovers Elusive Black Hole in Star Cluster: NPR

Hubble Space Telescope Discovers Elusive Black Hole in Star Cluster: NPR


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The Omega Centauri star cluster contains millions of stars. The movement of some of the stars suggests that there is a medium-sized black hole at its center.


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Astronomers have used the Hubble Space Telescope to find evidence of a hard-to-detect type of black hole, one that is about 8,000 times more massive than our sun.

What makes this black hole special is its size, according to a report About the discovery in the journal nature.

It’s much more massive than ordinary black holes, the kind that form when a dying star collapses in on itself. But it’s also not as big as the supermassive black holes that lurk at the center of galaxies and can contain hundreds of thousands to millions of suns.

Scientists have long been searching for intermediate-sized black holes like this new one, because finding them could shed light on the many ways black holes can form and why some grow into giant monsters.

But despite great efforts over the years, scientists have had no luck finding strong examples of black holes in the so-called intermediate-sized range, which includes any black hole between 100 and 100,000 times the mass of the Sun.

“So people wonder, are they hard to find because they simply don’t exist, or because they’re hard to discover?” he says. Maximilian Haberl Max Planck Institute for Astronomy, Heidelberg, Germany.

He and some colleagues recently decided to look for a star in a large, bright star cluster known as Omega Centauri. This densely packed spherical cloud of millions of stars lies about 17,000 light-years away.

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Black holes can’t be observed directly, because their gravity pulls in everything, including light. But researchers can look to see if a black hole’s gravity affects nearby objects, including stars.

The researchers learned that the stars in this particular cluster were being monitored continuously 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 instruments,” Haberl says.

Because the telescope had made high-quality observations dating back more than two decades, Haberle and his colleagues were able to accurately measure the motion of 1.4 million stars in the cluster.

“Our list of stars whose motions we have measured is much larger than any previous effort,” he says, adding that the stars “are all moving in random directions like a swarm of insects.”

Eventually, the researchers were able to identify seven stars in the center that were moving faster than the others. These stars were actually moving so fast that they should have been ejected from the cluster and disappeared forever.

The fact that it’s stuck and concentrated in the center “means that there must be something gravitationally pulling it so that it can’t escape,” Haberl says. “The only object that could be that massive would be an intermediate-mass black hole with a mass of at least 8,000 solar masses.”

He says the black hole is unlikely to be more than about 50,000 times the mass of the sun, because if it were, scientists would expect many more stars to be affected by its gravity.

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He points out that there was a precedent. Claim A medium-sized black hole candidate is likely to be found in this cluster dating back to 2008, but this has been disputed.

This time, he says, “I think our evidence is very strong” because of the additional years of data.

Furthermore, future observations are already planned with the James Webb Space Telescope, and this powerful telescope will be able to look for signs of gas heating up as it falls into the black hole.

“This is really exciting, isn’t it? This is only the second black hole where you can see individual stars orbiting the black hole,” he says. Jenny Greenan astrophysicist at Princeton University.

She points out that the only similar observation was Nobel Prize-winning work that saw stars circling the black hole at the center of the Milky Way, a supermassive black hole about four million times the mass of our sun.

“So I think this is really important. It’s a much lower mass black hole,” she says.

No one knows how a black hole of this size is created.

One possibility is that small black holes might merge together to form a larger black hole. Evidence for this comes from a statement From the gravitational waves produced by the collision of two black holes, an event that resulted in the emergence of a black hole about 150 times more massive than the Sun.

There is another possible way to grow intermediate-sized black holes, recently. Proposal Astronomers believe that many stars in a dense cluster like Omega Centauri may collide and form a single, very massive star. This massive star would later collapse into a medium-sized black hole.

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Understanding where intermediate-sized black holes are located and how they grow may help scientists understand the role they might play in the evolution of the larger black holes that lie at the heart of galaxies.

The newly discovered black hole “will tell us important information about how these large black holes form and grow,” Green says.

Such supermassive black holes appear to have appeared suddenly shortly after the universe began, a few hundred million years after the Big Bang.

That’s according to new observations made by the James Webb Space Telescope, which have left astronomers baffled about how the black hole managed to get so big so quickly.

Before these observations, Green says, she thought galaxies grew first and then black holes formed at their centers. “Now I’m less sure,” she says. “There’s some interesting evidence now that black holes are formed before their galaxies.”

Today’s intermediate-sized black holes may be leftovers from the early black hole formation process, and may offer clues about how it happened, Green says.

“Ultimately, to get a complete picture, we need more than one image, but this really opens the door,” she says.

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