What is the coefficient of mass gained/lost by a star in its first phase transitioning into a blackhole.

Does the blackhole have more or less mass than the star it was made from?

Thank you



For a star to be turned into a black hole it needs some inward force compressing the matter. In nature this force is gravity, pulling the star's material inward. An additional compression occurs when the star's outer material bounces off of the dense core and is expelled outwards.

This is the same type of process that happens during a core collapse supernova to form a neutron star. In fact if the star is massive enough to begin with, the remnant from the supernova will be a black hole.

In either case a great deal of the star's mass is expelled outward, leaving the resulting neutron star or black hole much less massive than it started.

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  • $\begingroup$ Just a small correction: The inward force compressing the matter is just gravity. The expulsion of matter outwards is a consequence of tapping into the gravitational potential energy. $\endgroup$ – kleingordon Jan 29 '16 at 22:57
  • $\begingroup$ Good point, I never mentioned the initial gravitational collapse. You are correct that the explosion is gravitationally driven, as the infalling material bounces of the dense core. The bounce does provide additional compression. I was going for a simple Newton's third law argument to ignore the gory details... maybe I ignored too many. (edited answer to mention gravity) $\endgroup$ – Paul T. Jan 31 '16 at 16:58

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