Mirror matter MACHOs

We propose that the massive compact halo objects (MACHOs) observed in the recent microlensing experiments with an apparent best fit mass of about 0.5M⊙ are objects made out of “mirror” baryonic matter rather than familiar baryons. Such a possibility arises naturally within the framework of mirror matter models proposed recently to accommodate the sterile neutrinos that seem necessary to solve all the neutrino puzzles simultaneously. We show that, for mirror matter parameters that fit the neutrino observations, the maximum mass of mirror stars is of order 0.5M⊙ and their main sequence lifetimes are much less than the age of the universe. They are likely to be black holes. Mirror matter machos have the advantage that they do not suffer from the problems encountered in the conventional red, brown or white dwarf interpretation. The calculations also apply to the question of how the world of familiar matter would be different if all fundamental mass parameters were.