Massive compact halo object

MACHO (short for "Massive Astrophysical Compact Halo Object " ) are compact celestial bodies from ordinary baryonic matter in the halo of a galaxy. You are an attempt at interpretation of the dark matter, as their total mass, the velocity distribution of stars in the galaxies could explain, which can be derived not only from the mass of the star.

Since by definition, the MACHO leave little or no light, they are not directly observable with telescopes from Earth. In question objects of planetary mass brown dwarfs or old, extinct and cooled stars come out. It is assumed that MACHOs have enough mass not to disintegrate already by tidal forces when they are in the proximity of other celestial bodies.

Detection by gravitational lensing?

The astrophysicist Bohdan Paczynski 1986 suggested the following way to prove the invisible MACHOs: An observer from Earth would be able to see it when a MACHO itself (eg a star) moves to a light source by located behind it. Then, namely the brightness of the light source changed in a way that can be calculated with the theory of general relativity: the MACHO forms a weak gravitational lensing.

Several research groups (among MACHO, OGLE, EROS ) have systematically observed a large amount of stars to see if they can find a light amplification due to the micro- lens effect. The Macho Collaboration claimed to have provided evidence for a number of MACHOs. Your extrapolation results MACHOs with up to 0.5 solar masses, which could explain a total of one-fifth of the dark matter in the Milky Way. Other researchers, however, doubt it.

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