Gamma rays can combine to form particles?

[Realitycheck]

In this article, they are claiming that antimatter is produced when black holes gobble up stars. What I have trouble with is when they say that matter is formed by waves.

 

As a black hole or neutron star destroys a star, tremendous amounts of radiation are released. Just as electrons and positrons emit the tell-tale gamma rays upon annihilation, so too can gamma rays combine to form electrons and positrons, providing the mechanism for the creation of the antimatter cloud, scientists think.

 

http://news.yahoo.com/s/space/20080111/sc_space/sourceofmysteriousantimatterfound

[Mr Skeptic]

But how would the antimatter get separated from the matter?

[Klaynos]

But how would the antimatter get separated from the matter?

 

A large magnetic field will do that just fine....

 

I'm not sure about "combining" 2 gamma rays to create a matter - anti-matter pair, but I do know you can use photons of sufficient energy to create the pairs, the idea comes from vacuum fluctuations that these pairs are being created and annihilated all the time on very very short time scales, and they just need a "kick" to have longer lifespans....

[swansont]

I think it's just an unfortunate use of the word "combine" by a reporter. Someone a little more science savvy would have asked/explained how the astronomers know this isn't primordial antimatter.

 

 

edit: another story

http://www.universetoday.com/2008/01/09/theres-a-lopsided-halo-of-antimatter-surrounding-the-centre-of-the-milky-way/

 

and there was a comment I read elsewhere that claims that there were 511 keV photons that were actually redshifted a fair amount, indicating significant gravity, hence the supposition that a neutron star or black hole is involved.

[Martin]

the best FREE article I've seen about this is here:

http://www.sciencedaily.com/releases/2008/01/080109173722.htm

 

the real article is in 10 January Nature magazine but I think it is pay-per-view

 

the point is that the cloud of 511 keV emission coincides with a region found to contain a lot of

hard X-ray binaries

more specifically hard low-mass X-ray binaries

 

the coincidence is circumstantial evidence that points the finger at the binaries being responsible somehow for the 511 keV.

 

this would mean that somehow the binaries are producing positrons which then get annihilated resulting in 511 keV.

 

 

a hard Xray binary means a binary star where one partner is a neutron star or black hole and is sucking in stuff from the other partner

 

as gas from the big partner spirals in towards the compact object it reaches high speed and temperature and radiates hard X-ray

 

but they don't understand how these abundant Xray binaries could be producing the positrons

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this region in central Milky producing a lot of 511 keV has first been noticed in 1970

and it has been a longstanding mystery

with many people offering many different explanations

 

this new work doesnt PROVE anything, what it does is exhibit a COINCIDENCE that there are a lot of these Xraybinaries where the radiation is coming from----so that it would be reasonable to try to figure out could these Xraybinaries be making it, and maybe to discover a possible mechanism.

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[Severian]

I think the word 'combine' is just fine in this context. Two photons annihilate to an electron-positron pair via a t-channel electron exchange.

 

It is this diagram rotated by 90 degrees anticlockwise

 

http://upload.wikimedia.org/wikipedia/en/5/59/ComptonScattering-s.svg

 

 

You can't do it with one photon since it wouldn't conserve energy.