A missing class of black holes may finally have an explanation
Gravitational-wave astronomy has turned black-hole populations into something measurable rather than purely theoretical. With hundreds of detections now on the books, astronomers can compare the masses of colliding black holes against long-standing predictions about how massive stars die. One of the most persistent puzzles has been the so-called forbidden gap: a range of stellar black-hole masses that theory said should be disrupted by an extreme kind of supernova. New research highlighted by Universe Today suggests the evidence for that gap is becoming harder to ignore.
The supplied source points to work led by Monash University arguing that stellar black holes above about 45 solar masses are unusually rare in the gravitational-wave record. That pattern aligns with the idea that stars in a certain mass range do not quietly collapse into black holes at all. Instead, they can be destroyed in pair-instability supernovae so violent that nothing is left behind.
Why the gap matters
This is not just an accounting exercise. Black-hole masses are a record of stellar evolution. If a wide band of masses is missing, something important happened during the final stages of those stars’ lives. The source explains the core mechanism: in the most massive stars, extreme conditions can create electron-positron pairs from energetic radiation inside the star. That reduces internal pressure and destabilizes the star.
Rather than collapsing into a black hole in the usual way, the star can explode catastrophically. In the pair-instability case described in the source, the explosion is powerful enough to leave no remnant at all. That would naturally carve out a gap in the black-hole mass distribution.
