  Motivated by theories of Neutral Naturalness, we argue that \emph{Mirror
Stars} are a generic possibility in any hidden sector with analogues of
Standard Model (SM) electromagnetism and nuclear physics. We show that if there
exists a tiny kinetic mixing between the dark photon and the SM photon, Mirror
Stars capture SM matter from the interstellar medium, which accumulates in the
core of the Mirror Star and radiates in the visible spectrum. This signature is
similar to, but in most cases much fainter than, ordinary white dwarfs. We also
show for the first time that in the presence of captured SM matter, a fraction
of dark photons from the core of the Mirror Star convert directly to SM
photons, which leads to an X-ray signal that represents a direct probe of the
properties of the Mirror Star core. These two signatures together are a highly
distinctive, smoking gun signature of Mirror Stars. We show that Mirror Stars
could be discovered in both optical and X-ray searches up to approximately
100-1000 light years away, for a range of well-motivated values of the kinetic
mixing parameter.
