Overview
- The Cardiff-led paper in Nature Astronomy studied 153 black hole mergers in the GWTC‑4 catalog.
- The team identified a lower-mass group that fits black holes born from single stars.
- A heavier group showed fast, misaligned spins, which points to black holes built by earlier mergers inside dense star clusters.
- The analysis finds a shift near about 45 solar masses, matching a predicted mass gap where collapsing stars should leave no black hole.
- The authors say more detections and better models could confirm rates, narrow the gap boundary, and even probe nuclear reactions in massive star cores.