Free Astronomy Magazine March-April 2022

16 MARCH-APRIL 2022 ASTRO PUBLISHING U sing the European Southern Observatory’s Very Large Tele- scope (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. This is the first time this detection method has been used to reveal the presence of a black hole outside of our galaxy. 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. The newly found black hole was spotted lurking in NGC 1850, a clus- ter of thousands of stars roughly 160,000 light-years away in the Large Magellanic Cloud, a neigh- bour galaxy of the Milky Way. “Similar to Sherlock Holmes tracking down a criminal gang from their mis- steps, we are looking at every single Black hole found hiding in star cluster outside our galaxy by ESO - Bárbara Ferreira T his artist’s impression shows a compact black hole 11 times as massive as the Sun and the five-solar-mass star orbiting it. 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. The distortion of the star’s shape is due to the strong gravitational force exerted by the black hole. Not only does the black hole’s gravitational force distort the shape of the star, but it also influences its orbit. 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. For this dis- covery, the team used the Multi Unit Spectroscopic Explorer (MUSE) instrument at ESO’s Very Large Telescope in Chile. [ESO/M. Kornmesser]