They detect a ‘small’ black hole outside the Milky Way 11 times bigger than the Sun

Posted: 12 Nov 2021 01:44 GMT

Scientists detected its influence on the motion of a nearby star using the Very Large Telescope (VLT) of the European Southern Observatory (ESO).

Astronomers have discovered a “small” black hole in NGC1850, a cluster of thousands of stars located about 160,000 light years in the Large Magellanic Cloud, outside the Milky Way.

The discovery came after detecting its influence on the motion of a nearby star using the Very Large Telescope (VLT) of the European Southern Observatory (ESO). It is the first time that this detection method has been used to reveal the presence of a black hole outside our galaxy.

“We observe each and every one of the stars in that cluster and, like Sherlock Holmes following the missteps of a criminal gang with his magnifying glass, we try to find some evidence of the presence of black holes, albeit without seeing them directly“, says Sara Saracino, of the Astrophysical Research Institute of the John Moores University of Liverpool (United Kingdom), who has led this research.

According to the study, this would represent only the first “criminal”, who, despite being classified as “small”, is about 11 times more massive than ours. It is also the first time that a black hole has been found in a young star cluster young, only about 100 million years old.

Previously, small stellar-mass black holes have been detected in other galaxies by the brightness of the X-rays they emit when absorbing matter, or by the gravitational waves that are generated when black holes collide with each other or with neutron stars. Nevertheless, most do not give away their presence through X-rays or gravitational waves.

“The presence of the vast majority can only be dynamically revealed,” says Stefan Dreizler, a member of the team based at the University of Göttingen (Germany). “When a black hole forms a system with a star, it will affect the motion of the star in a subtle but detectable way, so with sophisticated instruments, we will be able to find them.”

The researchers suggest that the method could be used in the future to discover hidden black holes in the Milky Way or nearby galaxies and to help shed new light on how these mysterious objects form and evolve.