First dormant black hole discovered is thought to be a 'needle in a haystack'

Astronomers have seen in the galaxy adjacent to our Milky Way what they call the cosmic “needle in the haystack” – 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 one differs from all other known black holes in that it is “quiet X-ray” – it doesn’t emit the intense X-ray radiation that indicates it devours nearby matter with a strong gravitational pull – and it doesn’t. born in the explosion of a star called a supernova.

Black holes are extremely dense objects with such strong gravity that even light cannot escape.

This one, with a mass at least nine times that of our sun, was detected in the Tarantula Nebula region of the Great Magellanic Cloud galaxy and is located about 160,000 light-years from Earth. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).

A very luminous and hot blue star with a mass about 25 times that of the sun orbits this black hole in a stellar marriage. This so-called binary system is named VFTS 243. The researchers believe the companion star will eventually also become a black hole and be able to merge with another.

Inactive black holes, considered relatively common, are difficult to detect because they interact very little with the surrounding environment. Many of the previously proposed candidates have been debunked by further study, including by members of the team that discovered this one.

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

“This is the first object of its kind found after astronomers searched for decades,” said astronomer and study co-author Kareem El-Badry of the Harvard & Smithsonian Center for Astrophysics.

The researchers spent six years observing from the Chile-based Southern European Observatory’s Very Large Telescope.

There are different categories of black holes. The smallest, as recently detected, are called stellar-mass black holes formed by the collapse of massive individual stars at the end of their life cycles. There are also medium-mass black holes as well as large supermassive black holes at the center of most galaxies.

“Black holes are essentially dark objects. They don’t emit any light. Therefore, to detect black holes, we usually look at binary systems where we see one glowing star moving around a second undetected object,” said the co-authors. study by Julia Bodensteiner, a postdoctoral researcher at the European Southern Observatory in Munich.

It is usually assumed that the collapse of a massive star into a black hole is associated with a powerful supernova explosion. In this case, a star perhaps 20 times the mass of our sun blows some of its material into space in its death throes, then collapses on its own without an explosion.

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

“The system’s orbit is almost perfectly circular,” said Shenar.

Had a supernova occurred, the force of the explosion would have kicked the newly formed black hole in a random direction and produced an elliptical orbit rather than a circular orbit, he added.

Black holes can become merciless voraciously, swallowing up any material – gas, dust, and stars – wandering in their gravitational pull.

“Black holes can only become merciless voraciously if something is close enough to them that they can devour them. Normally, we detect them if they receive material from a companion star, a process we call accretion,” Bodensteiner said.

Shenar added, “In so-called dormant black hole systems, the companion is far enough away that matter 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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