A Solar-System Window for Hidden Stellar Companions

This research explores the possibility of a hidden stellar or substellar companion to the Sun, located at hundreds or thousands of astronomical units, which would be electromagnetically dark but detectable through gravity. The study constructs a mass-distance map using existing planetary constraints and suggests that such an object would need to be a gravitationally bound structure rather than a typical dark matter halo draw. It proposes that a hidden-sector star, bright in dark photons, could fit within the allowed mass and distance window, offering a benchmark for future investigations.