Hardly any astronomical phenomenon is so mystified as black holes. Sometimes they make it possible to travel between different worlds, then again they are the offspring of hell or a possible means of super-fast transport. At a distance of less than 1,600 light-years from Earth, scientists have now discovered a candidate for the black hole closest to Earth to date. The object is orbited by a star in the constellation Ophiuchus, which resembles our Sun, they report in the journal "Monthly Notices of the Royal Astronomical Society". There is no plausible astrophysical scenario "that can explain the orbit and is not related to a black hole," they write. With the help of the novel method used, the team hopes to make further such discoveries in the coming years.
Black holes are objects whose mass is concentrated on an extremely small volume. Extremely massive versions with the million to billion-back solar mass are probably in the centers of all large galaxies, as the team around Kareem El-Badry from the Max Planck Institute for Astronomy in Heidelberg and the Harvard-Smithsonian Center for Astrophysics explains in Cambridge. Smaller stellar specimens that represent the final state of the development of massive stars are significantly more common. In the Milky Way alone, there are an estimated 100 million of them - but so far only a few have been confirmed.
The research group had used data from the GAIA spacecraft to the European Space Authority ESA, and in addition, targeted measurements were made with telescopes. Tiny position shifts of the star reveal the presence of the accompanying object. The "Gaia BH1" baptized black hole is less than half as far away as the nearest record holder so far, it said. It has a mass of around ten solar masses and is circled by a sun -like star with a round of 185.6 days. The distance to each other corresponds approximately to the distance between the earth and the sun. If the property was ten of the solar mass, it would inevitably shine much brighter than its companion. Instead, neither the Gaia data nor follow-up observations show light of such a second star.
The Astrometry mission GAIA is designed for high-precision measurements of star positions. Where two objects circle each other, each usually describes a small ellipse in the sky. With the rail data so -called double star systems, the scientists searched for candidates for a black hole. "There have been many alleged discoveries of such systems, but almost all of them were later refuted," said El-Badry loudly "This is the first clear detection of a sun-like star in a wide orbit around a black hole stellar mass in our galaxy."
"Gaia BH1" is a spectacular and at the same time mysterious find. It is not easy to explain how such a binary star system could have arisen at all, the scientists explain. The predecessor star, which later became a black hole, would have had a mass of at least 20 solar masses. This necessarily means that its lifespan must have been very short, on the order of a few million years. If the other star had formed around the same time, the massive star would have turned into a supergiant and bloated into space far beyond the common orbit of the stars, before the other star even had the time to become a real ("main-sequence") star with hydrogen fusion in the core. "All theoretical models that allow for survival predict that the massive star should have landed on a much narrower orbit than is actually observed." Thus, the discovery points to a gap in the understanding of how such systems arise in the first place.
The scientists now hope that the next large GAIA data publication, which is not expected before the end of 2025, enables dozens of similar systems to be possible-and helps to solve the puzzle by the development of the double star system.
