Astronomers discover rare black hole 'unlike any other'

A rare "missing link" black hole has been found in the Milky Way's large nearest galactic neighbor, a new study reveals.

Astronomers say the black hole has an "intermediate mass" and is the third rare type of black hole to come to light recently.

Described as "unlike any other", the black hole was found in a star cluster called B023-G078 in the Andromeda galaxy.

Also known as Messier 31 or M31, Andromeda is the closest large spiral galaxy to our galaxy, the Milky Way.

This newly discovered black hole has a mass 100,000 times greater than our Sun, making it smaller than the black holes found at the centers of galaxies (supermassive black holes), but larger than the black holes that are born when stars explode (stellar black holes).

One theory is that intermediate-mass black holes could be the seeds from which supermassive black holes grow.

The black hole was found hidden inside B023-G078, a huge star cluster in Andromeda with a solar mass of 6.2 million. The left panel shows a wide-field image of M31 with the red box and an inset showing the location and image of B023-G78 where the black hole was found.

Andromeda is the closest major galaxy to our galaxy, the Milky Way. Andromeda's diffuse light is caused by the hundreds of billions of stars that make it up. The several different stars that surround the Andromeda image are actually stars in our galaxy that are far ahead of the background object.

The three types of black hole

Stellar: Five to several tens of solar masses

Intermediate mass: 100 to 100,000 solar masses

supermassive: Millions to billions of solar masses

The new study, published in The Astrophysical Journal, was based on data from the Near-Infrared Integral Field Spectrograph (NIFS) on the Gemini North Telescope in Hawaii.

Astronomers measure the mass of a black hole by following the motion of gas and dust swirling around it.

This can be done at many wavelengths, for example by measuring the positions of stars orbiting close to a black hole at optical wavelengths.

Study author Anil Seth, an associate professor of astronomy at the University of Utah, said the finding fills a gap between very large and very small black holes known to exist.

"We have very good detections of the largest stellar-mass black holes up to 100 times the size of our sun and supermassive black holes in the centers of galaxies that are millions of times the size of our sun," he said.

“But there is no measure of black between these, that's a big gap. This discovery fills the void.

The study was based on data from the near-infrared integral field spectrograph (NIFS, pictured) on the Gemini North telescope in Hawaii.

Shown on the right side of this image is the Gemini Observatory on top of the Mauna Kea volcano. In the background is the Canada France Hawaii telescope

STAR CLUSTERS

As the name suggests, star clusters are groups of hundreds to millions of stars that share a common origin, all gravitationally bound together over several billion years.

There are two types of star clusters: open and globular. Globular clusters are dense balls of around a million ancient stars, all held together by gravity. Open clusters are much younger and smaller than globular clusters.

According to experts at Penn State University, open clusters are typically a few tens of millions to hundreds of millions of years old, while globular clusters are typically between 12 and 13 billion years old.

The black hole was found hidden inside B023-G078, a huge star cluster in Andromeda with a solar mass of 6.2 million.

Long thought to be a globular star cluster, the researchers argue that B023-G078 is instead a bare core, a remnant of a small galaxy that fell into a larger one and had its outer stars stripped away by forces. gravitational.

What is left behind is a tiny, dense core orbiting the larger galaxy, and at the center of that core, a black hole.

"Previously, we found large black holes inside massive bare cores that are much larger than B023-G078," said lead author Renuka Pechetti of Liverpool John Moores University.

“We knew that there must be smaller black holes in lower-mass bare cores, but there has never been direct evidence.

"I think this is a pretty clear case that we have finally found one of these objects."

A globular cluster has a characteristic light profile that is the same shape near the center as it is in the outer regions.

But B023-G078 is different: the light in the center is round and then gets flatter as it moves out.

The chemical composition of the stars also changes, with more heavy elements in the center stars than those near the edge of the object.

"Globular star clusters form at basically the same time," Professor Seth said.

'Instead, these stripped cores may have repeated formation episodes, in which gas falls into the center of the galaxy and forms stars.

'And other star clusters can be pulled toward the center by the galaxy's gravitational forces.

“It's kind of a dumping ground for a lot of different things. So stars in bare cores will be more complicated than in globular clusters. And that's what we saw in B023-G078.'

The researchers hope to see more bare cores that may contain more intermediate-mass black holes.

In September 2020, researchers in Australia working as part of an international collaboration studying gravitational waves reported the first direct observation of an intermediate-mass black hole.

About 150 times heavier than our Sun, it was born from the merger of two smaller (although still very large) black holes 17 billion light-years away.

BLACK HOLES HAVE A GRAVITATIONAL ATTRACTION SO STRONG THAT EVEN LIGHT CAN'T ESCAPE

Black holes are so dense and their gravitational pull is so strong that no form of radiation can escape from them, not even light.

They act as intense gravity sources that suck in dust and gas around them. Its intense gravitational pull is thought to be what stars in galaxies orbit around.

How they form is still poorly understood. Astronomers think they may form when a huge cloud of gas up to 100,000 times larger than the sun collapses into a black hole.

Many of these black hole seeds then merge to form much larger supermassive black holes, which are found at the center of all known massive galaxies.

Alternatively, a supermassive black hole seed could come from a giant star, about 100 times the mass of the sun, that eventually becomes a black hole after it runs out of fuel and collapses.

When these giant stars die, they also go 'supernova', a huge explosion that expels matter from the star's outer layers into deep space.