Dark compact planets

Abstract

We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron-star matter and white-dwarf material. We consider non-self annihilating dark matter with an equation of state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses and radii from a few Km to few hundred Km for weakly interacting dark matter which are stabilized by the mutual presence of dark matter and compact star matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses and radii of few hundred Km. These objects could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed $2\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$ pulsars set limits on the amount of dark matter inside neutron stars which is, at most, $1{0}^{\ensuremath{-}6}\text{ }\text{ }{\mathrm{M}}_{\ensuremath{\bigodot}}$.