<p>To put a formal answer to this question, a black hole made of anti-matter would be indistinguishable from a matter black hole. Black holes are dubious objects, but it seems likely that it makes no sense to talk about an "anti-matter black hole" as once the matter goes into the black hole, be it matter or anti-matter, it ceases to have properties that define it as matter or anti-matter. The <a href="https://en.wikipedia.org/wiki/No-hair_theorem" rel="nofollow">No-Hair Theorem</a> for black holes states that, among a few other properties, a black hole is defined only by it's mass and net charge. The matter state of individual particles which fell into the black hole play no part in that description.</p>

<p>In fact, there is a vigorous debate as to <a href="https://en.wikipedia.org/wiki/Black_hole_information_paradox" rel="nofollow">whether or not "information" is conserved for black holes</a>. E.g., if an anti-matter particle fell into a black hole, could you, at a later time, pull out a particle of the same properties or would you get out something of completely randomly new properties, not tied to the original matter. This in part plays into your question because it indicates that there is still a lot of uncertainty regarding the loss of information (including if the particle is anti-matter or matter) as particles fall into a black hole and whether not feeding anti-matter into a black hole actually makes it an anti-matter black hole or just simply a black hole.</p>

CC BY-SA 3.0
2016-08-31T18:48:57.367Z
So really, it doesn't even *matter* what the black hole is made of.
Sir Cumference
CC BY-SA 3.0
2016-08-31T14:29:43.290Z
2016-08-31T14:29:43.290Z
zephyr
<p>Would a black hole from a star made of anti-matter be the same as a blackhole made of ordinary matter?.</p>

CC BY-SA 3.0
2016-08-31T11:44:37.607Z
Pretty much, yes.   They would be the same.   But what would happen if a regular matter black hole and an anti-matter black hole were to collide?   :-)
userLTK
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2016-08-31T11:46:47.587Z
that was going to my next question :), would they annihilate each other or merge?
Fanana
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2016-08-31T11:59:57.623Z
Would they?  (I'm not trying to be difficult, just encouraging you to try to work it out before asking).
userLTK
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2016-08-31T12:56:13.693Z
@userLTK How can he possibly work it out? No one could know the answer to that question.
zephyr
CC BY-SA 3.0
2016-08-31T13:51:51.693Z
@zephyr true, there's some uncertainty, but a matter anti-matter explosion inside an event horizon would be irrelevant.   Gamma rays couldn't escape.   Unless the model used is one where material never falls inside a black hole, which isn't the common model, then would be no annihilation.      But there would be gravitational waves, which would happen with any 2 colliding black holes.
userLTK
CC BY-SA 3.0
2016-08-31T13:53:19.637Z
@Fanana That's an interesting one. Theoretically you can make a black hole out of pure light as light still has mass, so two merging matter and antimatter black holes may very well merge into a black hole made of gamma radiation.
Logan
CC BY-SA 3.0
2016-08-31T14:01:49.727Z
@userLTK It's even harrier than that. Does the concept of anti-matter even have meaning inside a black hole? Are particles really distinct entities or do they form into one composite "super-particle" at the singularity which no longer retains the individual properties of the individual particles? I think talking about colliding anti-matter and matter inside a black hole is at best a question without meaning.
zephyr
CC BY-SA 3.0
2016-08-31T14:36:45.927Z
@zephyr but that's only relevant to the first question, it's (mostly) not relevant to the 2nd question.
userLTK
CC BY-SA 3.0
2016-08-31T14:46:25.913Z
@userLTK I assume by 2nd question, you're talking about what if you collide an anti-matter and matter black hole, to which I say, my comment is relevant. I'm basically trying to say that there's no such thing as an anti-matter black hole (or matter black hole for that matter). There's just black holes.
zephyr
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2016-09-01T21:28:30.137Z
@userLTK but what would an anti-black hole do? :)
El Bromista
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2016-09-02T02:04:55.760Z
@ElBromista  That was kind of my point, and I meant it more as a little joke than anything else.   The no hair theorem means that it doesn't matter what a black hole is made of, it's just mass and curved space-time.  An anti-matter black hole wouldn't do anything.   Now if you ask the question regarding information or charged black holes (which I don't really understand), then it gets more complicated, but, with the most basic theory, it doesn't matter what a black hole is made of, an antimatter-matter explosion inside the black hole wouldn't be visible to those outside the black hole.
userLTK
<astrophysics>
Is a black hole made from a anti-matter star the same as a ordinary black hole?
Fanana
# Is a black hole made from a anti-matter star the same as a ordinary black hole?

(Asked by: username_0 on 2016-08-31)

Would a black hole from a star made of anti-matter be the same as a blackhole made of ordinary matter?.

**Tags:** astrophysics

> **Comments:**
> **username_1**: Pretty much, yes.   They would be the same.   But what would happen if a regular matter black hole and an anti-matter black hole were to collide?   :-)  
> **username_0**: that was going to my next question :), would they annihilate each other or merge?  
> **username_1**: Would they?  (I'm not trying to be difficult, just encouraging you to try to work it out before asking).  
> **username_2**: @username_1 How can he possibly work it out? No one could know the answer to that question.  
> **username_1**: @username_2 true, there's some uncertainty, but a matter anti-matter explosion inside an event horizon would be irrelevant.   Gamma rays couldn't escape.   Unless the model used is one where material never falls inside a black hole, which isn't the common model, then would be no annihilation.      But there would be gravitational waves, which would happen with any 2 colliding black holes.  
> **username_3**: @username_0 That's an interesting one. Theoretically you can make a black hole out of pure light as light still has mass, so two merging matter and antimatter black holes may very well merge into a black hole made of gamma radiation.  
> **username_2**: @username_1 It's even harrier than that. Does the concept of anti-matter even have meaning inside a black hole? Are particles really distinct entities or do they form into one composite "super-particle" at the singularity which no longer retains the individual properties of the individual particles? I think talking about colliding anti-matter and matter inside a black hole is at best a question without meaning.  
> **username_1**: @username_2 but that's only relevant to the first question, it's (mostly) not relevant to the 2nd question.  
> **username_2**: @username_1 I assume by 2nd question, you're talking about what if you collide an anti-matter and matter black hole, to which I say, my comment is relevant. I'm basically trying to say that there's no such thing as an anti-matter black hole (or matter black hole for that matter). There's just black holes.  
> **username_4**: @username_1 but what would an anti-black hole do? :)  
> **username_1**: @ElBromista  That was kind of my point, and I meant it more as a little joke than anything else.   The no hair theorem means that it doesn't matter what a black hole is made of, it's just mass and curved space-time.  An anti-matter black hole wouldn't do anything.   Now if you ask the question regarding information or charged black holes (which I don't really understand), then it gets more complicated, but, with the most basic theory, it doesn't matter what a black hole is made of, an antimatter-matter explosion inside the black hole wouldn't be visible to those outside the black hole.  

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## 1 answers

### Answer by username_2 on 2016-08-31. Score: 4

To put a formal answer to this question, a black hole made of anti-matter would be indistinguishable from a matter black hole. Black holes are dubious objects, but it seems likely that it makes no sense to talk about an "anti-matter black hole" as once the matter goes into the black hole, be it matter or anti-matter, it ceases to have properties that define it as matter or anti-matter. The [No-Hair Theorem](https://en.wikipedia.org/wiki/No-hair_theorem) for black holes states that, among a few other properties, a black hole is defined only by it's mass and net charge. The matter state of individual particles which fell into the black hole play no part in that description.

In fact, there is a vigorous debate as to [whether or not "information" is conserved for black holes](https://en.wikipedia.org/wiki/Black_hole_information_paradox). E.g., if an anti-matter particle fell into a black hole, could you, at a later time, pull out a particle of the same properties or would you get out something of completely randomly new properties, not tied to the original matter. This in part plays into your question because it indicates that there is still a lot of uncertainty regarding the loss of information (including if the particle is anti-matter or matter) as particles fall into a black hole and whether not feeding anti-matter into a black hole actually makes it an anti-matter black hole or just simply a black hole.

> **Comments:**
> **username_5**: So really, it doesn't even *matter* what the black hole is made of.  

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