An international team of scientists, including one from Poland, has discovered a “dormant” black hole with a stellar mass in the Large Magellanic Cloud – our neighboring galaxy. This discovery was reported by ESO and the Astronomical Observatory of the University of Warsaw. Interestingly, among the authors of the discovery is a group of scientists who have so far refuted similar discoveries made by other groups. The European Southern Observatory (ESO) statement noted that they are even called “black hole police”. But this time, astronomers have found such an object themselves – and announced it in Nature Astronomy.
While a similar black hole candidate has been proposed before, this time it has been pointed out that it is the first “sleeping” stellar-mass black hole to be unambiguously detected in a galaxy other than the Milky Way.
A stellar-mass black hole forms at the end of a massive star’s life and collapses under the influence of its gravity. If this happens in a binary system, the result will be a bright star and a black hole orbiting each other. In the event that a black hole does not emit high-energy X-rays from its vicinity, astronomers say it is “asleep.” It is difficult to find sleepers, as they hardly interact with their surroundings.
The researchers looked at nearly a thousand massive stars in the Tarantula Nebula region of the Large Magellanic Cloud. Scientists from the group led by Dr. Tomer Schnarer of the University of Amsterdam were looking for stars with black holes as companions. It turns out that one of the systems, called VFTS 243, consists of a hot blue star with a mass 25 times the mass of the sun and an invisible object with a mass at least 9 times the mass of the sun. Various hypotheses about the nature of the invisible component were tested and it turned out that the only possible explanation was the presence of a dormant black hole.
The discovery was made through six years of observations using the Multi-element Spectrophotometer (FLAMES) instrument on ESO’s VLT at Paranal Observatory in Chile.
Also of interest to the research are observations made by Polish astronomers from the University of Warsaw as part of the OGLE project with the Warsaw Telescope at Las Campanas Observatory in Chile. These observations continued for many years and showed that the brightness of the system has slight changes during the orbital period due to the gravitational deformation of the main star by the black hole. The observed effects are fully consistent with the model predictions.
The black hole appears to have formed without a previous supernova explosion, and has completely collapsed. This is evidenced by the absence of explosive remnants and a semicircular orbit. This is consistent with the hypothesis that the most massive stars end their lives in this way.
Scientists expect that the second star will also turn into a black hole one day, and we will be dealing with a system of two black holes that are slowly tightening their orbit due to the emission of gravitational waves. The merging of these black holes into one will occur in the very distant future, in tens or even hundreds of billions of years.
It is believed that thousands of dormant black holes may be present in the Milky Way and the Magellanic Clouds. In this context, it should be noted that another publication has recently been accepted for publication in “Astronomy and Astrophysics”, presenting the results of a similar discovery: a promising candidate for a stellar-mass black hole in the system HD 130298 in the Milky Way.
Among the authors of the new publication, which appeared in “Nature Astronomy”, there are many Polish names: Mariusz Gromadzki, Patryk Iwanek, Szymon Kozłowski, Przemysław Mróz, Pawe Pietrukowicz, Radosław Poleski, Krzysztof Ryrobicki, Skronowron. , Igor Sozinsky, Misha K. Shimansky, Andrei Udalsky, Krzysztof Olachek, Marcin and Rona.
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