Energy from colliding supermassive black holes (matter/antimatter)

[Matthias]

How much energy would be released if two supermassive black holes the size of Sagittarius A* collided, but one was made of antimatter? If this happened at the position of our galactic core, would we even notice it?

[grant hutchison]

I think it depends on the geometry of the collision, since the energy is radiated as gravitational waves. But there's a value that can't be exceeded, since the area of the combined event horizon can't be less than the area of the two separate event horizons, according the the Second Law of black hole mechanics.
The "content" of the black hole is irrelevant: a black hole formed from antimatter has exactly the same properties as one formed from matter.

Grant Hutchison

[astromark]

As the two massive objects accelerated and spiraled into each other the new greater mass would simply grow in strength and its combined mass would simply engulf a greater area. I suspect we might not ever know of it. As the central bulge of the galaxy would not have changed.
Like the event horizon would have just grown some... The safe orbital geometry would have moved some... What did you think ?

[grant hutchison]

Like the event horizon would have just grown some... The safe orbital geometry would have moved some... What did you think ?

I think supermassive objects accelerating hard put out a lot of gravitational waves. The theory behind black hole mergers is good enough to provide a "signature" pattern of gravitational radiation we could expect to detect when black holes merge.

Grant Hutchison

[Matthias]

I think it depends on the geometry of the collision, since the energy is radiated as gravitational waves. But there's a value that can't be exceeded, since the area of the combined event horizon can't be less than the area of the two separate event horizons, according the the Second Law of black hole mechanics.
The "content" of the black hole is irrelevant: a black hole formed from antimatter has exactly the same properties as one formed from matter.

Grant Hutchison

OK...as an unrelated question, is it possible that all the antimatter "missing" from the Big Bang is currently tied up in black holes?

[caveman1917]

OK...as an unrelated question, is it possible that all the antimatter "missing" from the Big Bang is currently tied up in black holes?

Theoretically, yes. However there are some strong arguments against it.
1. There should thus be as much antimatter in black holes as there is observable matter. The unsuccesful search for MACHOs (as an explanation for dark matter), makes this extremely unlikely.
2. This would just move the question from matter-antimatter asymmetry to why antimatter is more likely to form black holes in the first place, it doesn't really help to get us closer to an answer.
3. To have this result, the matter-antimatter distribution would have to be highly heterogeneous to start with.

[WayneFrancis]

I'm with grant and astro on this. 2 black hole of similar size will merge. If they where made of matter and anti-matter would make no difference. The reaction should happen completely within the event horizon which would be 2x as big as each of the single black holes.

There is also a few more things to think about.
It is quite possible that the matter and anti-matter would no longer be in matter form but some type of energy at that point rendering the possibility of inhalation moot.

As to black holes containing much of the missing antimater the problem is 3 fold.
1 There is no reason to think that anti-matter would clump to black holes more then normal matter would.
2 BH's are known to suck in large amounts of matter anyway meaning that a good amount of their total mass would be from normal matter
and
3 the total amount of mass/energy in BH is no where near what should be expected to solve the asymmetry issue.
That is my understanding.

[mugaliens]

Matter-antimatter collisions release approximately half their energy in the form of photons, but upwards of 50% is released in the form of neutrinos. However, as mentioned, any collision of a matter BH with an antimatter BH would be contained behind the event horizon, so neither photons nor neutrinos would escape.

The movement, particularly any spiraling of the BHs would create gravity waves which are theoretically detectible.

[Nereid]

Matter-antimatter collisions release approximately half their energy in the form of photons, but upwards of 50% is released in the form of neutrinos. [...]

I didn't know that.

Can you give some examples please?

[trinitree88]

I didn't know that.

Can you give some examples please?

Nereid. Nor I. I've only seen gamma rays, net. I'd like to see the examples, too. thanks for the DTD references while I'm at it. pete

[Matthias]

Matter-antimatter collisions release approximately half their energy in the form of photons, but upwards of 50% is released in the form of neutrinos. However, as mentioned, any collision of a matter BH with an antimatter BH would be contained behind the event horizon, so neither photons nor neutrinos would escape.

The movement, particularly any spiraling of the BHs would create gravity waves which are theoretically detectible.

OK, so if the matter or antimatter of the black holes were converted into photons and neutrinos, what is there left to be "holding up" the event horizon? What if enough mass is converted into photons and neutrinos to drop the total mass of the BH below the minimum mass required to form a black hole in the first place? Would it remain a black hole of smaller size, or become something else?

[loglo]

E=mc^2...... matter is energy.... there is no escape!

[Jeff Root]

Matthias,

Every object free-falling into a black hole gets pulled farther and farther
away from every other free-falling object in the radial direction. That
means a particle falling in at one moment and another particle falling in
a tenth of a second later on the same path get farther and farther apart
as they fall toward the center. So it may not be possible for two massive
particles to ever meet inside the event horizon. I think that is a question
not answerable by current theory.

Curvature of spacetime (gravity) is caused by the presence of energy.
We think of mass as the cause of gravity because mass is a very dense
form of energy, as indicated by the famous equation loglo just posted.
In fact, it is the most dense form of energy there is. It would take an
awful lot of light to equal even a small mass. So if a huge quantity of
ordinary matter and an equal quantity of antimatter annihilated each
other, the fantastically enormous quantity of light released would give
the same spacetime curvature-- the same gravity-- as the combined
masses.

-- Jeff, in Minneapolis

[WayneFrancis]

Black holes gain mass when photons enter them...even photons from the CMBR. It is just a VERY small amount of mass and even this is enough to counter act the Hawking radiation happening from the black hole.

1kg of photons = 1kg of feathers = 1kg of U238....it is all the same to the black hole...in fact...the black hole would eat the photons much easier then the latter 2. Black holes are very messy eaters when they eats large amounts of Fermions.