# Smallest mass of star to be a black hole? [duplicate]

It seems to me that I forgot the smallest mass of a star and its angular momentum in order to form a black hole.

So I know that electron degeneracy pressure is overcome if the core is 1.4 solar masses, and neutron degeneracy pressure is overcome if the core is 3 solar masses, but if the neutron star is spinning fast enough, it can have a maximum mass of about 4 solar masses. But then, this is just the core of the star. How large does this star have to be in order to form a black hole, and how fast would its spin need to be in order to avoid forming a blitzar?

I've looked on google and bing but to no avail.

Help is appreciated!

Thank you!

Max0815

Please stop trying to make this a duplicate.

Why: How large does this star have to be in order to form a black hole, and how fast would its spin need to be in order to avoid forming a blitzar?

• Out of interest, where did you find the 4 solar mass number for the maximum neutron star mass? ps. Neutron degeneracy pressure is not what supports neutron stars; especially massive ones. – ProfRob Mar 1 '19 at 21:44
• @RobJeffries neutron degeneracy pressure does support neutron stars, but the spin has some effect too. Blitzars are neutron stars that have too much mass and should be black holes, because neutron degeneracy pressure can't hold out, but they have so fast spin that the neutron star keeps stable. I found the limit on a video I watched sometime ago, but im not sure what video that was. – Max0815 Mar 1 '19 at 22:18
• That neutron stars are not supported by neutron degeneracy was established nearly 80 years ago by Oppenheimer & Volkhoff. They showed that the maximum mass of a NS supported by NDP is just 0.75 solar masses. All neutron stars are more massive than this. – ProfRob Mar 2 '19 at 0:09
• @RobJeffries yeah I realized. It was a misconception I had when I started leaning about astronomy year and years ago. It's held apart by the spin and nuclear forces. – Max0815 Mar 2 '19 at 5:15
• Clearly the first half of your question is a duplicate. If not, then clarify why not, or remove it and clarify what you mean by a "blitzar" and what "its" is in your last sentence. – ProfRob Mar 2 '19 at 19:35