Inert stellar-mass black holes, which form when massive stars reach the end of their lives, are hard to spot, because they don’t interact much with their surroundings. This is because, unlike most black holes, inert holes do not emit high levels of X-rays.
While it was thought to be a fairly common cosmic phenomenon, previously this type of black hole It has not been “unequivocally detected outside our galaxy,” according to the team of American and European researchers involved in the study.
The newly discovered black hole, called VFTS 243, has a mass at least nine times the mass of our Sun. It orbits a hot blue star that weighs 25 times the mass of the Sun, making it part of a binary system.
“It’s incredible that we hardly know any dormant black holes, given how commonly astronomers believe they exist,” study co-author Pablo Marchant, an astronomer at KU Leuven in Belgium, said in a press release.
The research was published in the scientific journal Nature Astronomy on Monday.
elimination process
To find the black hole, which is not directly observable, astronomers looked at 1,000 massive stars (each weighing at least eight times the mass of the Sun) in the Tarantula Nebula in the Large Magellanic Cloud, a galaxy near the Milky Way.
Co-author Tomer Schnarer, who was at KU Leuven in Belgium when the study began and is now a Marie Curie Fellow at the University of Amsterdam in the Netherlands, said the discovery was made through a process of exclusion.
The researchers first identified stars that were part of binary systems — stars moving around a cosmic companion. Next, they searched for binary systems where the companion was not visible, Careful analysis eventually showed that VFTS 243 was a dormant black hole, he explained via email.
“What we’re seeing here is a star that weighs regarding 25 times the mass of our sun, and it moves periodically (every 10 days or so) around something ‘invisible’ that we can’t see in the data,” Schnarer said.
“The analysis tells us that this other ‘thing’ must be at least 9 times the mass of our sun. The main part of the analysis is disposal: what might weigh nine solar masses, and not emit any light? The black hole is the only possibility we have left (this one, or an invisible fat alien…)”.
“There may be more out there, but only for this hole can we unambiguously show the presence of a black hole,” Schnarer said.
The black hole was found using six years of observations by the Large Fiber Multi-Element Spectrometer (FLAMES) instrument on ESO’s Very Large Telescope. FLAMES allows astronomers to observe more than a hundred objects simultaneously.
black hole police
Some of the study’s 40 authors are known in astronomy circles as black hole police, according to the news release, because they debunked many other discoveries of other black holes.
More than 10 discoveries of binary black hole systems in the past two years have been disputed, the newspaper said. However, they were confident that their finding was not a “false alarm”.
“We know what the challenges are, and we’ve done everything we can to rule out all other options,” Shanar said.
The research team said they called for scrutiny of their latest findings.
“In science, you’re always right until someone proves you wrong, and I can’t know that that’s never going to happen — I just know that none of us can spot an analysis flaw,” Schnarer said.
