Antimatter and Antistars?

payndz asks: "I'm currently writing an SF novel, and came up with a weird thought for a piece of background flavour that, if there's any scientific basis for it, might get expanded into a larger element. The most up-to-date theories for the creation of the universe 13.7 billion years ago (give or take...) suggest that at the Big Bang, matter *and* antimatter were created. Over time, the fact that there was slightly more matter than antimatter means that mutual annihilation has left a universe of matter. (I'm not going to open up the whole can of 'dark matter' worms, unless somebody wants to...). I have a 'what if' question, which since Hubert Farnsworth isn't around I thought would get some good responses here: what if, rather than antimatter being annihilated by matter in the universe at large, there are 'clumps' of both matter and antimatter making up the universe? Since our clump is almost entirely matter, billions of LY away could there be galaxies made up of antimatter?More to the point, what physical properties would these galaxies have? Would a star made of antimatter function in the same way as a matter star, and would its emissions be made of antiparticles? Can you have anti-photons, and if you could, what impact would they have on any matter they illuminated? Could life evolve in an antimatter environment?"

Comments

Don't land on one :-)

[oren]

Larry Niven had this great short story where Elephant looks for the most unusual piece of real estate in the known space... nicknamed "Cannonball", it is a solar system zooming *very fast* through our galaxy. While that is unusual by itself, it isn't the *most* unusual thing about it, as you can guess.

Luckily for him his pilot is a coward, so they don't land :-)

Seriously, the existrance of large amount of anti matter (whole galaxies of it) isn't _that_ far fetched. Consider that the original big-bang universe is made out of hot plasma. A blob of matter pressed against a blob of anti matter will create a terribly violent reaction in the interface zone; this would act as a "wall" repelling both matter and anti-matter away from it, preserving them as seperate regions. Also, any electrical current flowing through the plasma will tend to separate matter and anti-matter. Given the whole universe is expanding madly in the duration it is possible that ant-matter "islands" survived.

AFAIK (IANAP) anti-matter galaxies/stars would be indistinguishible from normal-matter ones. Photons don;t care whether they are created by matter fusion or anti-matter fusion, etc.

Some info as i remember

[Sklivvz]

First of all, there's basically no difference between a galaxy (or a physical body) made of matter and antimatter... Actually you wouldn't be able to tell. The major physical difference is the charge of particles (e.g. anti-electrons, or positrons, have +ve charge) but of course you wouldn't be able to tell since you would call +ve charge -ve and vice versa.

Secondly, according to the theories you mentioned, there's basically very little chance that large lumps of antimatter were formed during the big bang, since most of the annihilation would have taken place at a stage when all the matter was condended in a very small place, and therefore the distribution of antimatter would be quite uniform (so you wouldn't have a galaxy of am here and one of normal matter there).

Thirdly, there are no antiphotons. Photons are the antiparticles of themselves!

Hope it helps!