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The Question

(Submitted May 16, 1997)

How serious is the hypothesis about anti-stars? (Are there some experiments, theories, etc.?)

I study physics and a year ago I did a kind of homework concerning CAPRICE experiment (balloon flight) who's aim is to measure the flux of positrons, antiprotons and possibly, search for lighter anti-nuclei. As far as I understood, one of the reasons for this kind of experiments is the fact that previous data of the flux of antiparticles showed higher flux than predicted from several models. There was a hint, that antistars may exist which emit anti-protons and positrons as Sun emits solar wind. Well, when I mentioned this to my professor, he smiled and acted as it was an astrology I was talking about, not astrophysics.

Are the results of CAPRICE experiments already known?

The Answer

We don't know for sure that we live in a matter Universe, only that individual superclusters of galaxies are each made of either matter or antimatter. (Otherwise anti-matter atoms in the gas that pervades a supercluster would interact with the matter parts of it, or vice-versa, giving an easily identifiable energy emission).

We may live in a matter supercluster within a segregated matter-antimatter Universe. (Most people don't think that it's likely, but we don't have enough data to rule it out. That's why people are still looking.) If we find any anti-atoms, they must come from anti-stars from a antimatter supercluster a long way away.

Your can find information and results from CAPRICE on a number of web sites:

http://ida1.physik.uni-siegen.de/caprice.html
- has references to papers

http://ida1.physik.uni-siegen.de/caprice2.html
- describes the next generation CAPRICE

David Palmer, Jim Lochner, and Karen Smale
for the Ask an Astrophysicist

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