MACHO (Massive Astronomical Compact Halo Object)

A MACHO (Massive Astronomical Compact Halo Object) is a hypothetical compact object, large numbers of which might account for a significant fraction of the dark matter in the galactic halos of large galaxies, including that of our own. If MACHOs exist they could take the form of black holes, neutron stars, red dwarfs, brown dwarfs, large rogue planets, or some other type of non-luminous body. A signature of these objects would be the occasional amplification of light from more distant sources by microlensing. No conclusions have yet been drawn about the existence or nature of MACHOs; however, various microlensing events detected by search efforts such as OGLE and the MACHO Project support the idea that invisible compact objects do exist in the Galaxy's halo.