# Mass of a black hole?

We know that a teaspoonfull of the mass of a black hole would weigh nearly a mountain on Earth. But when a star collapses into a black hole in a supernova. The pieces of the star fly off in the space. So does the mass of the star equal the mass of the black hole? Ideally it should not. But how much mass goes in to make the black hole and how much of the mass gets wasted or spread out in pieces in space?

• It depends on the explosion/collapse which is the reason it's hard to just give out numbers. But it is less than the previous mass of a star for the reasons you've already stated. – MaDrung Feb 10 '17 at 11:14
• It is difficult to say how much of the mass stays in the black hole as the process is violate. The calculation is very complicated. – Drake Marquis Feb 10 '17 at 11:41
• The mass of a black hole is at a singularity and is therefore infinitely dense. The usual quote is that a teaspoonful of a neutron star weighs as much as a mountain on Earth. en.wikipedia.org/wiki/Neutron_star – James Feb 10 '17 at 14:43
• If a star explodes and its "core" has at least 1.4 solar masses (Chandrasekhar limit, en.wikipedia.org/wiki/Chandrasekhar_limit) then the end of the star will not be a white dwarf but a neutron star or black hole depending on the mass of the core. As you pointed out the mass of the core will not be the mass of the star. – Alpha001 Feb 11 '17 at 7:58