Dormant black holes with star mass, which form when massive stars reach the end of life, are especially difficult to spot since they do not interact much with their surroundings. This is because, unlike most black holes, dormant holes do not emit high levels of X-rays.
While believed to be a fairly common cosmic phenomenon, this type of black hole used to be had not been “unambiguously discovered outside our galaxy,” according to the team of American and European scientists involved in the study.
The newly discovered black hole, called VFTS 243, is at least nine times the mass of our sun, and it orbits a hot blue star that weighs 25 times the mass of the sun, making it part of a binary system.
“It’s amazing that we hardly know of any dormant black holes, given how ordinary astronomers think they are,” said co-author Pablo Marchant, an astronomer at KU Leuven, a university in Belgium, in a press release.
To find the black hole, which cannot be observed directly, astronomers looked at 1,000 massive stars (each weighing at least eight times the mass of the sun) in the Tarantula nebula region of the Great Magellanic Cloud, a galaxy near the Milky Way. Road.
The discovery was made through an elimination process, said co-author Tomer Shenar, who worked at KU Leuven in Belgium when the study started and is now a Marie-Curie research fellow at Amsterdam University, in the Netherlands.
First, the scientists identified the stars that were part of binary systems – stars that moved around a cosmic companion. Then they looked for binary systems where the companion was not visible, and careful analysis eventually revealed that VFTS 243 was a dormant black hole, he explained via email.
“What we see here is a star that weighs about 25 times the mass of the sun, and moves periodically (every 10 days or so) around something ‘invisible’, which we can not see in the data,” said Shenar.
The analysis tells us that this second “thing” must be at least 9 times more massive than our sun. The main part of the analysis is elimination: what can weigh nine solar masses and emit no light? A black hole is the only possibility we have left (this, or a fat invisible alien …). ”
“There may be more in there, but only for this one could we show the presence of a black hole unambiguously,” Shenar said.
The black hole was found using six years of observations of the Fiber Large Array Multi Element Spectrograph (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 40 study authors are known in astronomy circles who black hole police, according to the press release, because they have disproved several other findings of other black holes.
The newspaper said that more than 10 discoveries of binary systems for black holes in the last two years were controversial. However, they were sure that their discovery was not a “false alarm”.
“We know what the challenges are, and we did everything in our power to rule out all other options,” Shenar said.
The research team said that they invited to investigate their latest findings.
“In science, you are always entitled to some proof that you are wrong, and I do not know that this would never happen – I just know that none of us can detect an error in the analysis,” said Shenar.