An elusive black hole has been discovered in a nearby galaxy for the first time, according to a new study based on observations from the European Southern Observatory’s (ESO) Very Large Telescope.

Dormant stellar-mass black holes, which form when massive stars reach the end of their lives, are especially difficult to detect because they have little interaction with their environment. This is because, unlike most black holes, sleepers do not emit large amounts of X-rays.

Although this type of black hole was considered a fairly common cosmic phenomenon, earlier was not “unequivocally detected outside of our galaxy,” according to a team of American and European researchers involved in the study.

The newly discovered black hole, dubbed VFTS 243, is at least nine times the mass of our Sun. orbits a hot blue star with 25 times the mass of the Sun, making it part of a binary system.

“It’s incredible that we barely know about any sleeping black holes, given how ordinary astronomers think they are,” study co-author Pablo Marchand, an astronomer at KU Leuven, a university in Belgium, said in a press release.

The study was published in the scientific journal Nature Astronomy on Monday.

To find a black hole that cannot be observed directly, astronomers studied 1,000 massive stars (each weighing at least eight times the mass of the sun) in the Tarantula Nebula region of the Large Magellanic Cloud, a galaxy located not far from the Milky Way. Path.

The discovery was made by elimination, said co-author Tomer Schenard, who worked at KU Leuven in Belgium when the study began and is now a research fellow at the Marie-Curie University at the University of Amsterdam in the Netherlands.

First, the researchers identified stars that were part of binary systems – stars moving around a cosmic companion. Then they looked for binary systems where the satellite was not visible, and careful analysis eventually showed that VFTS 243 was a sleeping black hole, he explained via email.

“What we’re seeing here is a star about 25 times the mass of our Sun that periodically (every 10 days or so) moves around something ‘invisible’ that we can’t see in the data.” Shenar said.

“Analysis tells us that this other ‘thing’ must be at least 9 times as massive as our Sun. The main part of the analysis is the exception: what can weigh nine solar masses and not emit any light? A black hole is the only possibility we have left (it’s either a fat invisible alien…).”

“There may be more, but only for this we were able to unambiguously show the presence of a black hole,” Shenar said.

The black hole was discovered during six years of observations with the Fiber Large Array Multi Element Spectrograph (FLAMES) instrument at ESO’s Very Large Telescope. FLAMES allows astronomers to simultaneously observe over a hundred objects.

According to the press release, some of the 40 authors of the study are known in astronomical circles as the black hole police because they disproved several other black hole discoveries.

The paper says more than 10 black hole binary discoveries over the past two years have been contested. However, they were confident that their discovery was not a “false alarm”.

“We know what the problems are and have done everything in our power to rule out all other options,” Shenar said.

The research team said they offered to scrutinize their latest findings.

“In science, you are always right until someone proves you wrong, and I cannot know that this will never happen – I only know that none of us can find a flaw in the analysis,” Shenar said.