Bulge and disk of a galaxy are immersed in massive
halo. Some researchers assume, that the basic mass of halo is contained not in
stars, but in the nonluminous (hidden) matter consisting of bodies with a mass,
intermediate between masses of stars and planets, or from fundamental particles,
which existence predict the theorists, but which should be discovered. The
problem of a nature of this substance — hidden mass — now occupies minds of many
scientists, and its solution can give a key to a nature of matter in the
Universe as a whole.
Specially for ThinkQuest.