Astrometric Residuals: Recovering a Planet's Signal

Most exoplanet-hunting techniques you'll see visualized — transits, radial velocity — infer a planet indirectly from a dip in brightness or a Doppler shift. Astrometry is more direct: it measures the star itself moving on the sky. But that raw motion is almost never dominated by the planet — it's dominated by the star's proper motion drifting across the galaxy and the Earth's own annual parallax loop. This simulator computes both, plus the star's genuine gravitational reflex wobble from Kepler's third law and the barycenter balance, and shows exactly what a real astrometric pipeline does: plot the messy raw track, then subtract the known proper motion and parallax to reveal (or fail to reveal, if noise is too high) the tiny periodic ellipse the planet actually leaves behind. Adjust planet mass, orbital distance, system distance, proper motion and per-epoch measurement noise to see which combinations let the signal clear the noise floor.