Failed Stars: Mass-Heavy, Density-Deficient Objects Above the Fusion Threshold

Conventional stellar physics predicts hydrogen fusion ignition above approximately 80 MJ . However, a population of objects exceeds this mass threshold yet fails to sustain fusion. These “failed stars” present a puzzle: sufficient mass, no ignition. Analysis reveals a common characteristic: low average density relative to fusing objects of comparable mass. We propose that mass alone is insufficient for fusion ignition—core density determines whether mass translates into fusion conditions. Objects with high mass but low density exist in “puffy” equilibrium states that never achieve core temperatures required for sustained hydrogen fusion.