February 29, 2024

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How to create a black hole from thin air

How to create a black hole from thin air

How many ways are there to leave this universe?

Perhaps the most famous director entails the death of a star. In 1939, physicist J. Robert Oppenheimer and his student Harlan Snyder, of the University of California, Berkeley, have shown that when a sufficiently massive star runs out of thermonuclear fuel, it collapses inward and continues to collapse forever, shrinking space, time, and light. It turned itself into what is today called a black hole.

But it turns out that a dead star may not be needed to form a black hole. Instead, at least in the early universe, giant clouds of primordial gas may have collapsed directly into black holes, bypassing their millions of years in stardom.

That's the tentative conclusion recently reached by a group of astronomers studying UHZ-1, a speck of light dating from not long after the Big Bang. In fact, UHZ-1 is (or was) a powerful quasar that shot fire and X-rays from a supermassive black hole 13.2 billion years ago, when the universe was not even 500 million years old.

In cosmological terms, this is unusually close, as a supermassive black hole could come into existence through star collapses and mergers. Priyamvada Natarajan, an astronomer at Yale University and the lead author of Paper published in the journal Astrophysical LettersShe and her colleagues confirm that they have discovered in UHZ-1 a new celestial type, which they call a supermassive black hole galaxy, or OBG. At its core, the OBG is a young galaxy anchored by a black hole that has become very large, very quickly. .

The discovery of this early quasar could help astronomers solve a related mystery that has puzzled them for decades. Almost every visible galaxy in the modern universe appears to contain at its center a supermassive black hole millions of billions of times the mass of the Sun. Where did those monsters come from? Is it possible for ordinary black holes to grow so quickly?

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Dr. Natarajan and her colleagues suggest that UHZ-1, and perhaps many supermassive black holes, started out as primordial clouds. These clouds may have collapsed into grains that were prematurely heavy, enough to initiate the growth of massive black hole galaxies. It's another reminder that the universe we see is governed by an invisible geometry of darkness.

“As the first OBG candidate, UHZ-1 provides compelling evidence for the formation of heavy proto-seeds from direct collapse in the early Universe,” Dr. Natarajan and her colleagues wrote. “It appears that nature creates BH seeds in many ways,” she added in an email, “beyond just the death of stars!”

“Bria has found a very interesting black hole, if true,” said Daniel Holz, a theorist at the University of Chicago who studies black holes.

He added: “It is simply too big and too early. It's like looking into a kindergarten classroom, and among all the 5-year-olds there is one who is 150 pounds and/or six feet tall.

According to the story astronomers keep telling themselves about the evolution of the universe, the first stars condensed from clouds of hydrogen and helium left over from the Big Bang. They burned hot and fast, quickly exploding and collapsing to form black holes 10 to 100 times the mass of the Sun.

Over the eons, successive generations of stars have formed from the ashes of previous stars, enriching the chemistry of the universe. The black holes left over from their deaths continued to merge and grow in some way, forming supermassive black holes at the centers of galaxies.

The James Webb Space Telescope, launched two years ago this Christmas, was designed to test this idea. It has the largest mirror in space, measuring 21 feet in diameter. Most importantly, it was designed to record the infrared wavelengths emitted by the light of the most distant and therefore oldest stars in the universe.

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But once the new telescope was pointed at the sky, it could see new galaxies so massive and bright that they defied cosmologists' expectations. Arguments have raged over the past two years over whether these observations actually threaten a long-standing model of the universe. The model describes the universe as consisting of a trace of visible matter, astonishing amounts of “dark matter,” which provides gravity to bind galaxies together, and “dark energy,” which pushes these galaxies apart.

The discovery of UHZ-1 represents an inflection point in these discussions. To prepare for future observations with the James Webb Space Telescope of a massive cluster of galaxies in the Sculptor constellation, Dr. Natarajan's team requested time at NASA's Chandra X-ray Observatory. The cluster's mass acts as a gravitational lens, magnifying objects behind it in space and time. The researchers hoped to get an X-ray glimpse of whatever the lens might be viewing.

What they found was a quasar powered by a supermassive black hole about 40 million times the mass of the Sun. Further observations by the Webb Telescope confirmed that it was 13.2 billion light-years away. (The Sculptor Cluster is located about 3.5 billion light-years away.) It was the farthest and oldest quasar ever discovered in the universe.

“We needed Webb to find this remarkably distant galaxy, and Chandra to find its supermassive black hole,” Akos Bogdan of the Harvard-Smithsonian Center for Astrophysics said in a press release. “We also took advantage of a cosmic magnifying glass that enhanced the amount of light we detected.”

The results indicate that supermassive black holes existed 470 million years after the Big Bang. That's not enough time to allow the black holes created by the first generation of stars — ranging from 10 to 100 solar masses — to grow that large.

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Was there another way for larger black holes to form? In 2017, Dr. Natarajan suggested that the collapse of primordial gas clouds could give birth to black holes 10,000 times more massive than the Sun.

“You can then imagine one of them later growing to form this small, early large black hole,” Dr. Holz said. As a result, he noted, “At every subsequent time in the history of the universe, there will always be some surprisingly large black holes.”

“The fact that these objects start out in hypermassive lives means they are likely to eventually evolve into supermassive black holes,” Dr. Natarajan said. But no one knows how that works. Black holes make up 10% of the mass of the early quasar UHZ-1, while they make up less than one-thousandth the mass of modern galaxies such as the giant galaxy Messier 87, whose black hole has a mass of 6.5 masses. One billion solar masses when its image was taken by the Event Horizon Telescope in 2019.

This suggests that the effects of complex environmental feedbacks dominate the growth and evolution of these galaxies and their black holes, causing them to accumulate more mass in stars and gas.

“In fact, these very early OBGs are transmitting and illuminating more information about the physics of the seed rather than subsequent growth and development,” Dr. Natarajan said. She added: “Although it has important implications.”

“It would certainly be great if that turned out to be what's happening, but I don't really know,” Dr. Holz said. “It will be a fascinating story regardless of how the mystery of early large black holes is solved,” he added.