"Every single detection we make will be important for our future understanding of stellar clusters and the black holes in them," says study co-author Mark Gieles from the University of Barcelona, Spain. This dynamical method used by Saracino and her team could allow astronomers to find many more black holes and help unlock their mysteries. "When they form a system with a star, they will affect its motion in a subtle but detectable way, so we can find them with sophisticated instruments." "The vast majority can only be unveiled dynamically," says Stefan Dreizler, a team member based at the University of Göttingen in Germany. However, most stellar-mass black holes don't give away their presence through X-rays or gravitational waves. The smoking gun that put the astronomers on the trail of this black hole was its gravitational influence on the five-solar-mass star orbiting it.Īstronomers have previously spotted such small, "stellar-mass" black holes in other galaxies by picking up the X-ray glow emitted as they swallow matter, or from the gravitational waves generated as black holes collide with one another or with neutron stars. This first "criminal" tracked down by the team turned out to be roughly 11 times as massive as our Sun. "The result shown here represents just one of the wanted criminals, but when you have found one, you are well on your way to discovering many others, in different clusters." "Similar to Sherlock Holmes tracking down a criminal gang from their missteps, we are looking at every single star in this cluster with a magnifying glass in one hand trying to find some evidence for the presence of black holes but without seeing them directly," says Sara Saracino from the Astrophysics Research Institute of Liverpool John Moores University in the UK, who led the research now accepted for publication in Monthly Notices of the Royal Astronomical Society.
The newly found black hole was spotted lurking in NGC 1850, a cluster of thousands of stars roughly 160 000 light-years away in the Large Magellanic Cloud, a neighbor galaxy of the Milky Way. The method could be key to unveiling hidden black holes in the Milky Way and nearby galaxies, and to help shed light on how these mysterious objects form and evolve. This is the first time this detection method has been used to reveal the presence of a black hole outside of our galaxy.
Using the European Southern Observatory's Very Large Telescope (ESO's VLT), astronomers have discovered a small black hole outside the Milky Way by looking at how it influences the motion of a star in its close vicinity. For this discovery, the team used the Multi Unit Spectroscopic Explorer (MUSE) instrument at ESO’s Very Large Telescope in Chile. By looking at these subtle orbital effects, a team of astronomers were able to infer the presence of the black hole, making it the first small black hole outside of our galaxy to be found this way. Not only does the black hole’s gravitational force distort the shape of the star, but it also influences its orbit. The distortion of the star’s shape is due to the strong gravitational force exerted by the black hole.
The two objects are located in NGC 1850, a cluster of thousands of stars roughly 160 000 light-years away in the Large Magellanic Cloud, a Milky Way neighbour. This artist’s impression shows a compact black hole 11 times as massive as the Sun and the five-solar-mass star orbiting it.
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