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How To Discover Mirror Stars

Non-minimal hidden sectors are an important generic possibility and arise in highly motivated theories like Neutral Naturalness. A fraction of dark matter could therefore have hidden interactions analogous to Standard Matter (SM) electromagnetism and nuclear physics. This leads to the formation of \emph{Mirror Stars}: dark-sector analogues of regular stars that shine in dark photons. We examine the visible signatures of Mirror Stars in observations for the first time. If the dark and visible photon have a small kinetic mixing, SM matter is captured in Mirror Star cores, giving rise to an optical signal similar to but much fainter than white dwarfs, as well as a separate X-ray signal that represents a direct window into the Mirror Star core. This robust and highly distinctive signature is a smoking gun of Mirror Stars and could be discovered in optical and X-ray searches.