Dark Matter
Dark Matter There is perhaps no current problem of greater importance to astrophysics and cosmology than that of "dark matter". The controversy, as the name implies, is centered on the notion that there may exist an enormous amount of matter in the Universe that cannot be detected from the light that it emits. The evidence of dark matter is from the motions of astronomical objects, specifically stellar, galactic, and galaxy cluster/super cluster observations. ... Hence we infer that there is non-luminous matter in the Universe, i. ... there is dark matter. Dark matter has important consequences for the evolution of the Universe. ... A parameter known as the "mass density" - that is, how much matter per unit volume is contained in the Universe - determines which of the three possibilities applies to the Universe. ... Dark matter candidates are usually split into two broad categories, with the second category being further sub-divided: baryonic and bon-baryonic. Then, under non-baryonic, hot dark matter (HDM) and cold dark matter (CDM) are its types. ... As leading possible candidates for baryonic dark matter, there are black holes (large and small), brown dwarfs (stars too cold and faint to radiate), sun-size MACHOs, cold gas, dark galaxies and dark clusters, to name only a few.