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Story summary
- UK scientists reported that gravitational-wave data reveal a second population of heavy black holes formed through prior mergers.
- They examined 153 reliable detections and found 34 especially massive events.
- Black holes ~40 solar masses show small, aligned spins, whereas those above ~45 solar masses have rapid, chaotic spins.
- Isobel M. Romero-Shaw of Cardiff University said the pattern matches repeated mergers in dense clusters, indicating heaviest black holes are built, not born.
