The critical threshold, known as the Tolman–Oppenheimer–Volkoff (TOV) limit, is the maximum mass that a neutron star can have before it can no longer support itself against gravitational collapse and becomes a black hole. The exact value of the TOV limit is not precisely known because it depends on the equation of state (EOS) of nuclear matter at extremely high densities, which is still an area of active research.
Current estimates place the TOV limit in the range of approximately 2 to 3 solar masses (M☉). If a neutron star's mass is below this limit, it can remain stable as a neutron star. If its mass exceeds this limit, it will likely undergo further collapse to become a black hole.
Various observations and theoretical models continue to refine our understanding of the TOV limit, but it generally falls within this estimated range.
