  The fundamental nature of dark matter is entirely unknown. A compelling
candidate is Twin Higgs mirror matter, invisible hidden-sector cousins of the
Standard Model particles and forces. This generically predicts mirror neutron
stars, degenerate objects made entirely of mirror nuclear matter. We find their
structure using realistic equations of state, robustly modified based on
first-principle quantum chromodynamic calculations. We predict their
detectability with gravitational waves and binary pulsars, suggesting an
impressive discovery potential and ability to probe the dark sector.
