Antimatter in the universe [duplicate]

Question

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• How would we tell antimatter galaxies apart? 1 answer

Is it possible that some parts of the universe contain antimatter whose atoms have nuclei made of antiprotons and antineutrons, sorrounded by antiprotons? If yes what can be the ways to detect this condition without actually going there? Or can we detect these antiatoms by identifying the light they emit as composed of antiphotons? What problems might actually we face if we go there? Need some help!

Answer 1

I believe one method is to search for antinuclei in cosmic rays emitted from an antimatter region of the universe. It's a bit tricky, however, to distinguish these from antimatter that's been indirectly produced (e.g. from the interaction of "normal" cosmic rays with matter in the atmosphere).

Unfortunately, looking for antiphotons rather than photons doesn't help since the photon is its own antiparticle. However, there are some possibilities to look for the signature of photons that would be produced in large matter/antimatter annihilations (see here for example). The paper also mentions tentative methods for using the photon polarization as an indicator of an antimatter source.