What is most of the mass of our galaxy?

Question

What is most of the mass of our galaxy?

Answer 1

Dark matter, but it can't be found.

Answer 2

Dark matter.  It makes up most of the mass of the universe by a factor of about 6 to 1, and it also makes up most of the galaxy although I'm not sure about that specific factor.

Dark matter is noticable by its gravitational effects but it's not known exactly what it is.  The stars are the only visible matter because they're luminous.  Theories for dark matter include MACHOS (massive compact halo objects; brown dwarfs or black holes, basically) and WIMPS (weakly interacting massive particles; some type of sub-atomic particle so far undetectable because it reacts weakly or not at all with normal matter)