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I just read When a star becomes a black hole, does its gravitational power become stronger? and it confused me a bit;

I always thought black holes are supermassive and that is why they bend space-time. But it is said therein that the black hole is less massive than the star that created it (and it seems logical if we think about that - indeed, the star exploded and released a lot of matter).

Thus my question: How can a black hole bend space-time more than the star which created it?

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It doesn't bend it more. It is just that the matter of the star is now concentrated in a very compact region of space. So, previously you could get only to the surface of the star but now as the star is very compact, you can get much nearer and thus you will experience a greater gravitational force.

I had a similar discussion here. Check it out and maybe your question will be answered.

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  • $\begingroup$ Actually, you can get nearer to the geometric center of the mass, which accounts for the higher local gravity field (and tidal forces). Note that at the same distance from the (center) of the black hole and the (center) of the star, the black hole's gravity will be lower. $\endgroup$ – dotancohen Sep 4 '14 at 7:46
  • $\begingroup$ "Black hole's gravity will be lower". How so? By losing mass during the supernova? $\endgroup$ – Yashbhatt Sep 4 '14 at 9:45
  • $\begingroup$ Exactly. For spherical objects the gravity felt depends on only the mass of the object and the distance from it's center (squared). Black holes are assumed to be spherical. $\endgroup$ – dotancohen Sep 4 '14 at 10:14
  • $\begingroup$ @dotancohen I din't mean it that way. You can check out the link I mentioned in my answer. $\endgroup$ – Yashbhatt Sep 4 '14 at 10:17

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