# What is the outcome of a matter-antimatter explosion

So let’s say you develop a matter- antimatter bomb and explode it out in deep space. What do you have at the end? I know it would lead to total annihilation of both particles and a release of massive amounts of energy but what form does that energy take? Would there be residual radiation? Would there be residual anything?

The energy is emitted as photons. Due to laws of conservation we will expect at least two photons to be emitted from an electron-anti-election collision. That means that the photons will have an energy of 511 keV each, which is X-ray energy.

It depends on the kind of antimatter you have. Electrons and positrons are what gets talked about most, in which case they go directly to gamma rays (extremely high-energy photons). But most (familiar) matter gets most of its mass from protons and neutrons, so that’s not what you’d get with (say) a boulder and an anti-boulder.

When a proton and an anti-proton annihilate, the first step is that they turn into three pions. If you’re lucky (about a 1 in 3 chance), those pions will all be neutral pions, which after a short while will decay into photons. Otherwise, you’ll get one each positive, negative, and neutral. The pi+ will in turn decay into a mu+ and a mu neutrino, and the mu+ will then decay to a positron, a mu antineutrino, and an electron neutrino. The pi- will follow the reverse of that path, to an electron, an electron antineutrino, and a mu neutrino and antineutrino. The electrons and positrons will then eventually find each other and annihilate into photons.

A neutron-antineutron annihilation will follow the same path as a proton-proton annihilation. You can also get an annihilation of one of each, which gets a bit messier: With a proton and an antineutron, the possible pions are a pi+ and two neutrals (2/3 chance) or two pi+ and a pi- (1/3 chance).

Once you’re down to photons and neutrinos, they’ll just speed away from the site of the explosion, and not decay or react with each other any further. The neutrinos, in fact, won’t do much of anything past that point, but the photons, if they hit anything else (like, say, a planet that has the bad fortune to be in the vicinity of the explosion) will probably heat it up (with all of the usual effects of heating something up a great deal very quickly).

All told, you end up with close to half of the energy being wasted in neutrinos, that don’t contribute at all to Earth-shattering-kabooming.

You can also get creation of particle-antiparticle pairs. This has been observed. So the explosion isn’t completely “clean”

I’m sure that if you only had enough neutrinos they would kill a few people, too.