Shell collapsar

A shell collapsar is a hypothetical compact astrophysical object, which might constitute an alternative explanation for observations of astronomical black hole candidates. Being of neutron star size (~11km), it strongly distorts light rays like a black hole, but has no central point-like singularity. Matter has collapsed onto the event horizon forming a shell there of ultra-high density. The model of the shell collapsar was first proposed by Trevor W. Marshall and allows the formation of neutron stars beyond the Tolman–Oppenheimer–Volkoff limit of 2.1 M☉.

A shell collapsar is void inside apart from intense gravitational field energy there. Newton's shell theorem does not apply, but Einsteinian gravitation in the highly non-linear regime. . Gravitational time dilation is extreme on its surface (just outside the event horizon), so that the accreting neutron matter freezes onto the outer shell, as described in the ‘frozar’ model Zakir conceives that outward gravitational forces arise in the interior and push inner matter into the ‘frozar’ shell.

The shell collapsar is a special case of a gravastar. With the gravastar, an exotic form of matter stabilizes the object with the equation of state of dark energy inside. The shell collapsar comes to a similar result with ordinary neutron star matter and simply Einstein's field equations describing intense gravitational energy density, comparable as E/c² to the neutron matter density.