<p>I believe when most scientists refer to the mass of a blackhole - i.e. a blackhole having the mass of a billion Suns, what they really mean is that the calculated gravitational pull of the blackhole is equivalent to that of such a mass would it exists at the location of the blackhole.</p>

<p>PS: Perhaps you could also bring some reference with respect to where exactly have you heard that 'It is said that in Blackhole 100% part of the mass is getting converted into energy'</p>

CC BY-SA 3.0
2014-05-02T03:14:30.387Z
2014-05-02T03:14:30.387Z
harogaston
<p>The truth is no one truly knows if 100% of the mass is being converted into energy. So without this assumption many other things are possible. Some think that since there is a constant flow of mass into the black hole, the conversion into energy is not keeping up with the rate the matter is being consumed, therefore the mass would remain substantially large.</p>

CC BY-SA 3.0
2014-05-01T10:16:50.760Z
I believe that in fact the conversion factor is at most ~ 42 % for a maximally spinning blackhole, and about 10 % for a non rotating one. Which is a lot more than nuclear energy ~ 0.05 %. cf http://www3.mpifr-bonn.mpg.de/staff/mmassi/lezione2WEdd.pdf
chris
CC BY-SA 3.0
2014-04-30T17:50:43.637Z
2014-04-30T17:50:43.637Z
user3138766
<p>It is said that in Blackhole 100% part of the mass is getting converted into energy. Then how come Blackhole is having mass ?</p>

CC BY-SA 3.0
2014-04-30T15:52:54.330Z
They maybe doing so but if you know their mass is inversely proportional to the amount of radiation they emit. So, for a black hole to be of zero mass it will have to emit radiation for a fairly large amount of time. See [Hawking Radiation](http://en.wikipedia.org/wiki/Hawking_radiation)
Yashbhatt
CC BY-SA 3.0
2014-04-30T22:27:47.803Z
In gravitational terms mass and energy are similar - see special relativity for E=mc^2 etc. Perhaps you could reframe your question?
adrianmcmenamin
CC BY-SA 3.0
2014-09-02T15:11:12.973Z
@AmitG Could you tell us your source?
HDE 226868
CC BY-SA 3.0
2014-09-03T16:35:57.350Z
@HDE226868 - I was watching Discovery channel and they were telling above thought in one of the episode. In yet another episode they were telling when star finishes it's fuel then it collapse into the center which creates hole in spacetime and star become Supernova. I still didn't understand, whether it is a hole in spacetime or big mass with little radius and having existance.
AmitG
<black-hole><supermassive-black-hole>
How can a Blackhole have mass?
AmitG
# How can a Blackhole have mass?

(Asked by: username_0 on 2014-04-30)

It is said that in Blackhole 100% part of the mass is getting converted into energy. Then how come Blackhole is having mass ?

**Tags:** black-hole, supermassive-black-hole
> **Comments:**
> **username_1**: They maybe doing so but if you know their mass is inversely proportional to the amount of radiation they emit. So, for a black hole to be of zero mass it will have to emit radiation for a fairly large amount of time. See [Hawking Radiation](http://en.wikipedia.org/wiki/Hawking_radiation)  
> **username_2**: In gravitational terms mass and energy are similar - see special relativity for E=mc^2 etc. Perhaps you could reframe your question?  
> **username_3**: @AmitG Could you tell us your source?  
> **username_0**: @HDE226868 - I was watching Discovery channel and they were telling above thought in one of the episode. In yet another episode they were telling when star finishes it's fuel then it collapse into the center which creates hole in spacetime and star become Supernova. I still didn't understand, whether it is a hole in spacetime or big mass with little radius and having existance.  

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## 2 answers

### Answer by username_4 on 2014-05-02. Score: 2

I believe when most scientists refer to the mass of a blackhole - i.e. a blackhole having the mass of a billion Suns, what they really mean is that the calculated gravitational pull of the blackhole is equivalent to that of such a mass would it exists at the location of the blackhole.

PS: Perhaps you could also bring some reference with respect to where exactly have you heard that 'It is said that in Blackhole 100% part of the mass is getting converted into energy'


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### Answer by username_5 on 2014-04-30. Score: 0

The truth is no one truly knows if 100% of the mass is being converted into energy. So without this assumption many other things are possible. Some think that since there is a constant flow of mass into the black hole, the conversion into energy is not keeping up with the rate the matter is being consumed, therefore the mass would remain substantially large.

> **Comments:**
> **username_6**: I believe that in fact the conversion factor is at most ~ 42 % for a maximally spinning blackhole, and about 10 % for a non rotating one. Which is a lot more than nuclear energy ~ 0.05 %. cf http://www3.mpifr-bonn.mpg.de/staff/mmassi/lezione2WEdd.pdf  

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