Hubble and Webb find Omega Centauri’s first stellar-mass black hole

Astronomers using more than 20 years of NASA Hubble Space Telescope archival data, plus recent James Webb Space Telescope observations, say they have identified the first stellar-mass black hole in Omega Centauri [13]. The object, dubbed oMEGACat BH-2, was found through astrometry rather than the usual radio, X-ray, or radial-velocity methods, and the team says the binary has a 94-year orbit [13]. Why it matters: This is a notable step in resolving a long-standing gap in what scientists expected to find inside Omega Centauri, where models suggest thousands of stellar-mass black holes should exist [13]. The result may refine theories of black hole formation in metal-poor environments and improve understanding of how black holes form binaries in dense clusters [13]. Key insights: The discovery combines Hubble astrometry from 2002 to 2023 with Webb near-infrared data to constrain the companion’s mass more precisely [13]. | The team says the black hole’s mass is 4.46 solar masses, ruling out the earlier neutron-star interpretation [13]. | Researchers say the binary likely formed dynamically, meaning the star and black hole did not start out together [13]. | The system’s long orbital period makes it the longest-period black hole binary known to date [13]. Cheatsheet facts: What changed: A black hole candidate in Omega Centauri was confirmed as the cluster’s first detected stellar-mass black hole using Hubble and Webb data [13]. | Why now: A long archive of Hubble measurements plus newer Webb observations gave the precision needed to measure the object’s motion and mass [13]. | Watch next: Look for the paper’s reception in The Astrophysical Journal Letters and any follow-up modeling on black hole formation in metal-poor clusters [13].