# How do we know Saturn is not made of anti-matter?

**URL:** <https://boards.straightdope.com/t/how-do-we-know-saturn-is-not-made-of-anti-matter/309012>\
**Category:** Factual Questions\
**Created:** [June 20, 2005, 6:39am UTC](https://boards.straightdope.com/t/how-do-we-know-saturn-is-not-made-of-anti-matter/309012 "2005-06-20T06:39:34Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\
**Post date:** [June 28, 2005, 7:04pm UTC](https://boards.straightdope.com/t/how-do-we-know-saturn-is-not-made-of-anti-matter/309012/21 "2005-06-28T19:04:29Z")

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> [@Mathochist](#):
>
> Hold on there, chief. There’s plenty of antimatter around from various nuclear decay processes and energetic collisions, as well as our own efforts.
> 
> More importantly, there’s no reason to assume that there was more of one than the other in the primordial universe, which by your logic would lead to everything annihilating and leaving only radiation. The catch is that you’re implicitly assuming perfect mixing here, which is completely unjustified. More likely is that (as yet unexplained) fluctuations led to certain areas being a bit more matter and other areas being a bit more antimatter. As the universe expanded these blew up along with it, and once the matter and antimatter annihilated some regions were left matter-heavy while others were left antimatter-heavy.
> 
> Now, where you’re on the right track is this: Saturn coalesced from the same cloud of dust and such that formed the sun and all the other planets, so it’s from the same kind of matter.

OK, you forced me to look it up. We know Saturn isn’t antimatter because if it were the solar wind’s reaction with Saturn would make it a strong gamma ray source[sup]1[/sup]. It isn’t, so it isn’t.

We are also pretty sure that our galaxy is entirely matter because the cosmic rays very rarely produce antihelium nuclei (alpha particles) when colliding with the interstellar gas. So the detection of even one alpha particle in the cosmic rays would indicate a source of antimatter somewhere in the galaxy. None has been detected so far. Anti protons are produced by the primary cosmic ray collisions with the gas and such particles are occasionally detected in secondary cosmic radiation.[sup]1[/sup]

Based on similar reasoning about other galaxies and clusters of galaxies it is thought that there is practically no permanent antimatter in the universe. There are occasional antimatter particles produced but these annihilate very quickly to produce gamma rays.

1. Antimatter article by Gary Stiegman of Ohio State University in _The Encyclopedia of Physics_.

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**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\
**Post date:** [June 28, 2005, 8:32pm UTC](https://boards.straightdope.com/t/how-do-we-know-saturn-is-not-made-of-anti-matter/309012/22 "2005-06-28T20:32:23Z")

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QUOTE=Demo]No, actually it leads to annihilation reactions, which release gamma rays…  
[/QUOTE]

Which in turn are a leading cause of Incredible Hulkism.

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