Black hole is the closest to earth, among the smallest ever discovered

Scientists have discovered one of the smallest black holes recorded – and the closest to Earth to date.

Researchers have called it ‘The Unicorn’, in part because it is the only one of its kind so far, and in part because it was found in the constellation Monoceros – ‘The Unicorn’. The findings will be published in the journal today, April 21 Monthly notices from the Royal Astronomical Society.

“When we looked at the data, this black hole – the Unicorn – just came to the fore,” said lead author Tharindu Jayasinghe, a doctoral student in astronomy at Ohio State University and a presidential fellow in Ohio.

The Unicorn is about three times the mass of our sun – small for a black hole. Very few black holes of this mass have been found in the universe. This black hole is 1,500 light-years from Earth, still within the Milky Way. And until Jayasinghe started analyzing it, it was essentially visible.

The black hole appears to be a companion of a red giant star, meaning the two are connected by gravity. Scientists cannot see the black hole – it is by definition dark, not only visually, but also according to the instruments that astronomers use to measure light and other wavelengths.

But in this case, they can see the black hole’s companion. The star is well documented by telescopic systems, including KELT, which is from the state of Ohio; ASAS, the forerunner of ASAS-SN, now running out of state of Ohio, and TESS, a NASA satellite searching for planets outside our solar system. Data on it were widely available, but not yet analyzed in this way.

When Jayasinghe and the other researchers analyzed the data, they noticed that something they could not see revolved around the red giant, causing the star’s light to change in intensity and appearance at different points around the orbit.

Something, they realize, attracts the red giant and changes shape. This traction effect, called tide distortion, gives astronomers a signal that something is affecting the star. One option was a black hole, but it would have to be small – less than five times the mass of our sun, and fall into a magnitude window that astronomers call the “mass gap”. Recently, astronomers consider it a possibility that black holes of that mass may exist.

“If you look at it differently, that’s what we do, you find different things,” said Kris Stanek, co-author of the study, professor of astronomy at the state of Ohio and university-leading academics. “Tharindu looked at this thing that so many other people were looking at, and instead of rejecting the possibility that it could be a black hole, he said, ‘Well, what if it could be a black hole? ? ‘

That tidal disruption is caused by the tidal force of an unseen companion – a black hole.

“Just as the moon’s gravity distorts the Earth’s oceans, causing the seas to bulge to and from the moon and produce high tides, the black hole twists the star into a football-like shape with one axis longer than the other. , “said Todd Thompson, co – author of the study, chairman of the Ohio Department of Astronomy and college students. “The simplest explanation is that it’s a black hole – and in this case, the simplest explanation is the most likely.”

The velocity of the red giant, the period of the orbit and the way in which the tidal force distorted the red giant, told them the mass of the black hole, which led to the conclusion that this black hole was about three solar masses, or three times that of the sun.

About the past decade, astronomers and astrophysicists have wondered if they did not find these black holes because the systems and approaches they use were not as sophisticated as finding them. Or, they wondered, do they simply not exist?

About 18 months ago, many members of this Ohio State research team, led by Thompson, published a scientific article in the journal. Science, which provides strong evidence that this type of black hole exists. That discovery motivated Jayasinghe and others, both in the state of Ohio and around the world, to seriously look for smaller black holes. And the evaluation led them to the Unicorn.

Finding and studying black holes and neutron stars in our galaxy is crucial for scientists studying space, because it tells them about the way stars form and die.

But finding and studying black holes is almost by definition difficult: individual black holes do not emit the same rays as other objects in space. It is electromagnetically quiet and dark according to scientific equipment. The most famous black hole was discovered because it cooperated with a companion, which created many X-rays – and the X-rays are visible to astronomers.

In recent years, more large-scale experiments have been launched to detect smaller black holes, and Thompson said he expects to discover more “mass gap” black holes in the future.

‘I think the field is moving here, to really map out how many low-mass, how many intermediate-mass and how many high-mass black holes there are, because every time you find one, it gives you a idea of ​​which stars are collapsing, which is exploding and which is in between, ‘he said.

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