Overview
- A team led by Matthew Whitaker reported in a paper published July 13 that they measured a dark companion of about 4.46 times the sun’s mass inside the Omega Centauri globular cluster, confirming it is a stellar-mass black hole named oMEGACat BH-2.
- Researchers tracked a visible companion star using more than 20 years of Hubble data (2003–2023) refined with JWST observations to map the star’s motion and infer the unseen object’s mass from its gravitational pull.
- The visible star completes an orbit every roughly 94 years, which is the longest orbital period recorded for a black hole–star binary and indicates the pair was likely captured by dynamical encounters in the dense cluster.
- The black hole’s mass lies in the 2.5–5 solar-mass 'mass gap' that has been scarce in gravitational-wave detections, a result that challenges models of how low-mass black holes and neutron stars form in metal-poor environments.
- Teams plan to mine archival Hubble and JWST data and use upcoming and ongoing surveys from Gaia and the Nancy Grace Roman Space Telescope to search for many more stellar-mass black holes and to map compact-object populations in clusters.