  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 predicts mirror neutron stars made
entirely of mirror nuclear matter. We find their structure using realistic
equations of state, robustly modified based on first-principle quantum
chromodynamic calculations, for the first time. This allows us to predict their
gravitational wave signals, demonstrating an impressive discovery potential and
ability to probe dark sectors connected to the hierarchy problem.
