Now i haven't loked up anything because i got too excited but i just watched a doco on the universe and how it is 2/3 dark matter so we can't see it all and this got me thinking.....Could there be dark matter galaxies and dark stars (that name Darkstar is copy protected by me BTW!). As we can't see dark matter there is no way to tell but who out there thinks there could be dark matter stars/galaxies?

If I'm not mistaken, the name Darkstar was copyrighted a LONG time ago. I think Mike Oldfield got it; it was the name of a song on >Tubular Bells II.

Not a bad theory, though. Dark matter is strange stuff, but it shouldn't be bothering us any. None of that here in the good ol' Milky Way... well, not until some physicist arse up at MIT makes some, and kills all of us. But not YET.

There are several candidates for the dark matter in the universe. You can split them in two groups: those from normal matter and those from exotic matter.

The normal matter candidates are made from normal matter, don't send out light. Among these candidates are planets, the remain of died stars (brown dwarfs, white dwarfs, black holes) and just your normal stone floating around. These structures can't explain all the dark matter, because there wasn't enough matter formed if our theories on the big bang are right.

Therefore scientists started looking into exotic matter. The first candidate are neutrino's. These particles are very difficult to detect, but have been proven. We know that if they have mass, they have very little mass. This is not really problem, since there so much neutrino's. A mass of 1/5000 of the electron mass would mean enough dark matter.

Some scientists have also offered stranger kinds of matter as a possibility for dark matter. They are called WIMPs (Weakly Interacting Massive Particles). These are all not proven to exist. Examples include neutralino's, axions and magnetic monopoles.

So, yes, there can be dark matter galaxies. These will be made up from planets and the remains of died stars though. Those galaxies would probably fall apart over time, because stars eject a lot of their mass when they die. Neutrino's and WIMPs don't interact a lot. They can't form structures (with other particles) as protons or neutrons. Therefore they can't form stars and galaxies.