<p>This answer addresses first the initial misconception <em>that the mass of black hole is greater than the mass of its parent star</em>. This is not true.  The gravity may be more intense, but the mass is <em>less</em>.</p>
<p>The black hole or neutron star that forms after a supernova would have a lower mass than the star that it formed from, as some of the matter of the star is expelled in the explosion.</p>
<p>The black hole or neutron star would have more extreme gravity, because the mass that remains is concentrated in a much smaller volume of space (perhaps collapsed to a singularity).</p>
<p>The strength of gravity depends on both the mass (below you) and the distance you are from the centre.  So a more massive star can have lower surface gravity than a small planet if that star is sufficiently large.  Betelgeuse has a mass five million times that of the Earth, but its surface gravity is much less, because it is so puffed up.</p>
<p>So your definition of mass is fine. Mass is the factor that gives a body inertia. It is the ratio of momentum to velocity.  If we give two bodies the same impulse then their mass is in inverse proportion to the resulting speed. Mass is also proportional to Energy, and through this to the curvature of spacetime and so gravitational effects.</p>

CC BY-SA 4.0
2021-08-12T19:27:19.210Z
2021-08-12T22:05:19.573Z
2021-08-12T22:05:19.573Z
James K
<p>Since high school, I've been told that the definition of mass is &quot;quantity of matter&quot; (which is absolutely wrong, I guess). If mass is actually a quantity of matter and it is a measure of inertia, when a giant-star dies, if it is massive enough to undergo a supernova, it could either transforms into a neutron star or a black hole. Now, in a supernova some amount of matter is lost, but how does the black hole manage to have such a greater mass than its parent star? Coming to the &quot;definition&quot;, where has the excess matter come from? I know it hasn't, in practice it is not the case and it is not possible. So what is the actual definition of mass? What quantity does the mass define? And what are the factors creating/affecting inertia?</p>

CC BY-SA 4.0
2021-08-12T16:10:52.403Z
Have you read the [Wikipedia](https://en.m.wikipedia.org/wiki/Mass) page?
franz_lyre
CC BY-SA 4.0
2021-08-12T16:14:04.040Z
@f_n_lyre  Its too complicated to my standards. :(
Kavin Ishwaran
CC BY-SA 4.0
2021-08-12T16:50:32.463Z
Hi! Are you asking, in principle, "what is mass?"... which is a more basic physics question. Or are you asking, what is the mass of neutron stars and of black holes, and how does supernova effect it?
Daddy Kropotkin
CC BY-SA 4.0
2021-08-12T16:51:36.880Z
You may find my answer here helpful https://astronomy.stackexchange.com/a/43452/23762
Daddy Kropotkin
CC BY-SA 4.0
2021-08-12T17:55:03.590Z
*"But How the Black hole manage to have such a huge mass than its Parent star?"* A black hole has *less* mass than its parent star.
PM 2Ring
CC BY-SA 4.0
2021-08-15T23:06:26.817Z
I’m voting to close this question because it probably belongs on Physics SE.
WarpPrime
CC BY-SA 4.0
2021-08-17T06:46:29.667Z
I’m voting to close this question because it's not about Astronomy
uhoh
<star><black-hole><mass><stellar-remnants>
What actually is the mass?
Kavin Ishwaran
# What actually is the mass?

(Asked by: username_0 on 2021-08-12)

Since high school, I've been told that the definition of mass is "quantity of matter" (which is absolutely wrong, I guess). If mass is actually a quantity of matter and it is a measure of inertia, when a giant-star dies, if it is massive enough to undergo a supernova, it could either transforms into a neutron star or a black hole. Now, in a supernova some amount of matter is lost, but how does the black hole manage to have such a greater mass than its parent star? Coming to the "definition", where has the excess matter come from? I know it hasn't, in practice it is not the case and it is not possible. So what is the actual definition of mass? What quantity does the mass define? And what are the factors creating/affecting inertia?

**Tags:** star, black-hole, mass, stellar-remnants
> **Comments:**
> **username_1**: Have you read the [Wikipedia](https://en.m.wikipedia.org/wiki/Mass) page?  
> **username_0**: @f_n_lyre  Its too complicated to my standards. :(  
> **username_2**: Hi! Are you asking, in principle, "what is mass?"... which is a more basic physics question. Or are you asking, what is the mass of neutron stars and of black holes, and how does supernova effect it?  
> **username_2**: You may find my answer here helpful https://astronomy.stackexchange.com/a/43452/23762  
> **username_3**: *"But How the Black hole manage to have such a huge mass than its Parent star?"* A black hole has *less* mass than its parent star.  
> **username_4**: I’m voting to close this question because it probably belongs on Physics SE.  
> **username_5**: I’m voting to close this question because it's not about Astronomy  

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## 1 answers

### Answer by username_6 on 2021-08-12. Score: 4 | Accepted answer

This answer addresses first the initial misconception *that the mass of black hole is greater than the mass of its parent star*. This is not true. The gravity may be more intense, but the mass is *less*.

The black hole or neutron star that forms after a supernova would have a lower mass than the star that it formed from, as some of the matter of the star is expelled in the explosion.

The black hole or neutron star would have more extreme gravity, because the mass that remains is concentrated in a much smaller volume of space (perhaps collapsed to a singularity).

The strength of gravity depends on both the mass (below you) and the distance you are from the centre. So a more massive star can have lower surface gravity than a small planet if that star is sufficiently large. Betelgeuse has a mass five million times that of the Earth, but its surface gravity is much less, because it is so puffed up.

So your definition of mass is fine. Mass is the factor that gives a body inertia. It is the ratio of momentum to velocity. If we give two bodies the same impulse then their mass is in inverse proportion to the resulting speed. Mass is also proportional to Energy, and through this to the curvature of spacetime and so gravitational effects.


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