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Hubble and Webb Pin Down First Stellar-Mass Black Hole in Omega Centauri

Measured at about 4.46 times the Sun’s mass from two decades of astrometry, the object challenges models of how low-mass black holes form in metal-poor star clusters.

Overview

  • University of Utah researchers published peer-reviewed results Monday reporting oMEGACat BH-2 as the first confirmed stellar-mass black hole in the Omega Centauri globular cluster.
  • The team combined more than 20 years of Hubble position measurements with recent JWST infrared data to track tiny shifts in a visible star’s position and calculate the unseen companion’s mass.
  • The companion is about 4.46 solar masses, too heavy to be a neutron star and sitting inside the 2.5–5 solar-mass ‘mass gap’ seen in gravitational-wave detections.
  • The visible star orbits on a roughly 94-year period, the widest known black hole–star binary, which points to a dynamical capture origin and a predicted survival time under one billion years in the crowded cluster.
  • Researchers are mining Hubble and JWST archives now and expect NASA’s Roman telescope and future Gaia releases to reveal many more such binaries, which will reshape estimates of black-hole populations and formation physics in dense star systems.