Rossiter-McLaughlin Effect: Exoplanet Spin-Orbit Alignment

This simulator renders a rotating star as a real-time 3D sphere Doppler-shaded by rigid rotation, then walks a transiting exoplanet across its disk along a chord tilted by the sky-projected spin-orbit angle λ. As the planet blocks alternating blueshifted and redshifted patches of stellar surface, the simulator computes the resulting anomalous radial-velocity curve exactly as spectrographs measure it during a real transit — the same Rossiter-McLaughlin signal astronomers use to discover that many hot Jupiters orbit misaligned, polar, or even retrograde relative to their host star's rotation. Adjust the obliquity, impact parameter, planet size and stellar rotation speed and watch the RV curve reshape live, from the classic antisymmetric S-curve of an aligned system to the flattened, single-signed anomaly of a polar orbit.