After star explodes it may turn into BH

[dedaNoe]

The stars always have smaller mass than the mass of the black hole that emerges out of their explosion.

How come?

Did the matter of the star accelerated near c when it turned into BH?

 

[Labguy]

The stars always have smaller mass than the mass of the black hole that emerges out of their explosion.

How come?

Did the matter of the star accelerated near c when it turned into BH?

It is the other way around; the black hole always has a smaller mass than the progenitor star. See the link for a good, generic explanation of supernovae and the rate of matter and energy expulsion.

http://www.astronomyinfo.pwp.blueyonder.co.uk/Supernova.htm#Type II

 

[Phobos]

Like labguy said, the mass of the BH is less than the star it formed from. The fusion reaction in the core of a star creates an outward pressure that counteracts the inward gravitational pressure. Once the star can no longer sustain the fusion process, the matter can be compressed down to either a white dwarf, a neutron star, or a black hole depending on how much matter is left.

 

[dedaNoe]

Damn me. I didn't know that. I always taught that BH are the most masive things in space.

 

[Phobos]

You're close.

Theoretically, black holes can be any mass (even tiny masses). The trick is getting the mass down to zero volume. This results in the most intense gravitational field (up close at least).

The typical idea of a black hole is one created from the core of a giant star. So, those black holes have masses that are on the order of stars.

However, "supermassive" black holes are being found in the center of many galaxies. These black holes are fed (mass added) by lots of galactic material instead of just the remains of 1 star. Astronomers have found supermassive black holes with masses that are millions or billions the times the mass of our sun. In that sense, they are one of the most massive objects in the universe.