Nuclear Reaction Defines the Abyss for Black Holes ⚡ экспресс
Gravitational-wave observations have once again drawn attention to the black hole mass gap and the ^12C(α,γ)^16O reaction, which sets the C/O ratio and influences stellar evolution toward pair instability. Constraints on S(300 keV) from population analysis remain model-dependent, as the lower edge of the gap is extracted from assumptions about multiparameter evolution. Here, the S-factor is revisited using refined ANC values for the 1−, 2+, and ground state of ^16O plus direct capture data. The results favor lower S(300 keV) values, ruling out very high ones needed by some population models. This yields a lower bound for the pair-instability gap for first-generation black holes at 61–75 M⊙. Thus, nuclear data point to a relatively high lower edge of the gap.
Gravitational waves have laid bare an abyss: black holes with masses between 60 and 120 Suns are almost never born. This chasm is carved out by pair-instability supernovae—explosions that leave not even a speck of the star. Whether the star falls into the abyss or survives on its edge depends on the reaction of carbon with helium, which governs the core composition.
This process is leisurely: even a tiny speedup would turn all carbon into oxygen, depriving the universe of life. Fred Hoyle first realized the reaction is tuned exquisitely finely, otherwise carbon would be hundreds of times scarcer. New data have narrowed the possible rates by nearly half. It turns out the edge of the abyss lies farther out than thought: the lightest ordinary black holes start at 61–75 solar masses. A shift of just a couple percent—and the boundary leaps by tens of masses.
🎯 The carbon-helium reaction is so slow that the slightest acceleration would deprive the universe of carbon-based life.