Theory 07/Compact object populations/Gravitational-wave detectors
The Mass Gap Is a Boundary
The absence of compact objects between roughly two and five solar masses is set by the ratio of explosion energy to envelope binding energy, so the gap is a physical boundary rather than an observational artefact.
01Mechanism
A progenitor either loses its envelope and forms a neutron star or retains it and collapses entirely; the ratio determines which, with nothing in between.
02Prediction
Detected masses should avoid the gap.
03Refutation
A confident detection inside the gap would remove the boundary argument.
04What makes it checkable
Gravitational-wave detections now measure component masses directly and independently of electromagnetic assumptions, so the gap can be mapped rather than inferred.
05Why it was not testable before
Masses were previously inferred from light, which is indirect; mergers now weigh the objects themselves.