The Physics of a Black Hole Merger: What Happens to Mass?

[beamthegreat]

TL;DR Summary

What would happen if a black hole made entirely from anti-matter merges with another black hole made from normal matter?

What would happen if a black hole made entirely from anti-matter merges with another black hole made from normal matter? Since most of the product left over from the annihilation is in the form of light (gamma rays) would the black hole lose mass?

 

[Dale]

You would just get a bigger black hole. The no hair theorem implies that there is no distinction between black holes made from different constituents.

 

[verbamour]

Even if the gamma rays were created, they would still be stuck in the black hole.

 

[OCR]

The no hair theorem. . .

Only applies to Picard. . .

In this situation, the lots of hair theorem would apply. . .

The simple fact is. . . the Klingons would abscond with it to power their warp core. Trust me! .

.

 

[Edwina Lee]

I thought that the joining of an anti-matter particle with a normal particle of the same mass results in 0 mass, and the energy released is $2mc^2$ where m is the mass of each particle.
So as 2 black holes of opposite matter approach each other, we should start to see energy release caused by anti-particle collisions with normal particles before their event horizons meet.
The event horizon would expand and change shape as the holes approach into a sort of bulging tube linking the 2 holes. Matter annihilation could be seen on the surface of the event horizon and beyond, until the holes merge unceremoniously.

 

[Dale]

2 black holes of opposite matter

. There is no such thing. As I mentioned above the no hair theorem doesn’t permit this. Black holes have only mass, charge, and angular momentum. There is no matter vs antimatter distinction for black holes.

 

[Edwina Lee]

This is what you said in #2: "You would just get a bigger black hole. The no hair theorem implies that there is no distinction between black holes made from different constituents. "

Could you now explain why what you said is in conflict with what I said in #5:
<<"
I thought that the joining of an anti-matter particle with a normal particle of the same mass results in 0 mass, and the energy released is 2mc2 where m is the mass of each particle.
So as 2 black holes of opposite matter approach each other, we should start to see energy release caused by anti-particle collisions with normal particles before their event horizons meet.
The event horizon would expand and change shape as the holes approach into a sort of bulging tube linking the 2 holes. Matter annihilation could be seen on the surface of the event horizon and beyond, until the holes merge unceremoniously.
">>

 

[Dale]

Could you now explain why what you said is in conflict with what I said in #5:

Yes.

the joining of an anti-matter particle with a normal particle of the same mass results in ...
So as 2 black holes of opposite matter

The problem is that the analogy is false. Matter and antimatter particles do annihilate, but there is no such thing as an antimatter-black hole. It doesn’t make a difference if your black hole was originally formed using matter, antimatter, or even formed using only photons. The no hair theorem states that the black hole is the same, regardless of how it was formed or what source material was used in its formation.

A particle annihilates with an anti-particle, but there is no corresponding distinction for black holes. There simply are no “black holes of opposite matter”, so no description of how they behave is physically sensible.