Although not the first candidate, a researcher from the University of Sheffield says this black hole is “the first to be clearly detected outside our galaxy”. Researchers searched for black hole binaries for more than two years before finding what became known as VFTS243. Paul Crowther, professor of astrophysics at the university, described it as a “very exciting discovery” which comes after “a number of latent black hole candidates have been proposed”. Stellar mass black holes form when massive stars reach the end of their lives and collapse under their own gravity. In a system of two stars orbiting each other, this process leaves behind a black hole orbiting a bright companion star. The newly discovered latent black hole has a mass at least nine times the mass of Earth’s Sun and orbits a hot blue star that weighs 25 times more than the Sun. It has been observed in a neighboring galaxy by an international team of scientists. Their study – published in Nature Astronomy – suggests that the star that gave rise to VFTS243 disappeared without any sign of an associated supernova explosion. As part of the international research team, Crowther is working with Tomer Shenar from the Institute of Physics and Astronomy, who started the study at KU Leuven in Belgium and is now a Marie-Curie Fellow at the University of Amsterdam in the Netherlands. Confirming the possibility of what he called the “immediate collapse scenario,” that is, collapse without an explosion, Shenar believes this has “huge implications for the origin of black hole mergers in the universe.” A black hole is considered inactive if it does not emit high levels of X-ray radiation, as such black holes are usually detected. Quiescent black holes are difficult to detect as they do not interact much with their surroundings. VFTS 243 was found using six years of observations of the Tarantula Nebula by the Large Fiber Array Multi-Element Spectrograph instrument on the European Southern Observatory’s Very Large Telescope.
