Scientists find an exotic black hole thought to be a ‘needle in a haystack’

Scientists find an exotic black hole thought to be a ‘needle in a haystack’

An artist’s rendering of what the binary star system VFTS 243 — which contains an orbiting black hole and a large glowing star — might look like if we observed it up close is shown in this undated handout image . Located in the Tarantula Nebula in the galaxy Large Magellanic Cloud, the system consists of a hot, blue star 25 times the mass of our Sun and a black hole at least nine times the mass of the Sun. ESO/L. Calcada/Handout via REUTERS

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WASHINGTON, July 18 (Reuters) – Astronomers have spotted what they call a cosmic ‘needle in a haystack’ in a galaxy adjacent to our Milky Way – a black hole that is not only classified as dormant but appears to have been born without the explosion of a dying star.

Researchers said Monday this black hole differs from all other known black holes in that it is “X-ray silent” — it doesn’t emit powerful X-rays that suggest nearby material is being engulfed with its powerful gravitational pull — and that it didn’t give birth became a stellar explosion known as a supernova.

Black holes are exceptionally dense objects with gravity so intense that not even light can escape.

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At least nine times the mass of our Sun, it was discovered in the Tarantula Nebula region of the Large Magellanic Cloud and is about 160,000 light-years from Earth. A light year is the distance that light travels in one year, 5.9 trillion miles (9.5 trillion km).

An extremely bright and hot blue star about 25 times the mass of our Sun orbits this black hole in a stellar marriage. This so-called binary star system is called VFTS 243. The researchers believe that the companion star will eventually also become a black hole and could merge with the other.

Dormant black holes, which are thought to be relatively common, are difficult to spot because they interact very little with their surroundings. Numerous previously proposed candidates have been debunked by further study, including by members of the team that uncovered this one.

“The challenge is finding these objects,” said Tomer Shenar, a research associate in astronomy at the University of Amsterdam and lead author of the study, published in the journal Nature Astronomy. “We have identified a needle in a haystack.”

“It’s the first object of its kind to be discovered after astronomers searched for decades,” said Kareem El-Badry, astronomer and co-author of the study, of the Harvard & Smithsonian Center for Astrophysics.

The researchers used six years of observations from the Chile-based Very Large Telescope of the European Southern Observatory.

There are different categories of black holes. The smallest, like the newly discovered one, are so-called stellar-mass black holes, formed by the collapse of individual massive stars at the end of their life cycles. There are also intermediate-mass black holes, as well as the giant supermassive black holes that are at the center of most galaxies.

“Black holes are inherently dark objects. They don’t emit light. Therefore, to detect a black hole, we usually look at binary systems, in which we see a luminous star orbiting a second, unrecognized object,” he said study co-author Julia Bodensteiner, postdoctoral researcher at the European Southern Observatory in Munich.

Typically, the collapse of massive stars into black holes is thought to be accompanied by a violent supernova explosion. In this case, a star perhaps 20 times the mass of our sun blew some of its matter out into space in its death throes and then collapsed in on itself without exploding.

The shape of its orbit with its companion indicates the absence of an explosion.

“The orbit of the system is almost perfectly circular,” Shenar said.

Had a supernova occurred, the force of the explosion would have flung the newly formed black hole in a random direction, creating an elliptical rather than circular orbit, Shenar added.

Black holes can be mercilessly voracious, devouring any material—gas, dust, and stars—that shifts in their gravitational pull.

“Black holes can only gorge themselves mercilessly when they have something close enough to devour. We usually spot them when they receive material from a companion star, a process we call accretion,” Bodensteiner said.

Shenar added: “In so-called quiescent black hole systems, the companion is far enough away that material does not accumulate around the black hole to heat up and emit X-rays. Instead, it is immediately swallowed up by the black hole.”

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Reporting by Will Dunham, editing by Rosalba O’Brien

Our standards: The Thomson Reuters Trust Principles.

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