Astronomers confirm the existence of a lone black hole

Summary

A 2.′′⁡4×2.′′⁡0 WFC3 F814W field showing the OGLE-2011-BLG-0462 field at the final epoch in 2022. The source star and its brighter neighbor are labeled. A faint star lies just to the southeast of the neighbor, but it has little effect on astrometry of the source. For each star, an open green circle shows its location at E1 in 2011, and an open red circle marks its location at E11 in 2022. Stars in this Galactic-bulge field typically move about 1 WFC3/UVIS pixel (0.′′⁡040) over the course of 11 yr. Credit: The Astrophysical Journal (2025). DOI: 10.3847/1538-4357/adbe6e A team of astronomers at the Space Telescope Science Institute, working with one colleague from the University of St Andrews' Center for Exoplanet Science and another from the European Southern Observatory, has confirmed the existence of a lone black hole. In their paper published in The Astrophysical Journal, the group describes how they studied newer data regarding an object they had spotted several years ago to confirm its identity. In 2022, members of essentially the same team reported the discovery of what they described as a "dark object" moving through the constellation Sagittarius. They suggested it might be a lone black hole. Shortly thereafter, a second research team challenged that result, suggesting it was more likely a neutron star. After continuing to study the object, the original research team has found more evidence backing up their original claim that it is likely a lone black hole. Prior to this new finding, all the black holes that have been identified have also had a companion star—they are discovered due to their impact on light emitted by their companion star. Without such a companion star, it would be very difficult to see a black hole. The one identified by the team was only noticed because it passed in front of a distant non-companion star, magnifying its light and shifting its position in the sky for a short while. The research team made their initial observations using data ...