A planet orbits two stars (P-type). The binary pair revolves around their shared center of mass while the planet circles both. Stable only beyond a critical distance.
Binary System
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Circumbinary (P-type): Two stars orbit their shared center of mass while a planet orbits both. Try Kepler-16b for a stable configuration, or "Unstable" to watch the planet get ejected. The dashed circle marks the approximate stability boundary.
Lagrange Points: Sun–Jupiter system with a massless test particle. Switch to the co-rotating frame to see kidney-shaped tadpole orbits around L4/L5, or horseshoe orbits that alternate between leading and trailing. L1 and L2 are unstable—the particle drifts away within a few orbits.
Hierarchical (S-type): A planet orbits Star A while a distant companion Star B perturbs it. Watch the eccentricity chart to see secular oscillation from the companion's gravity. The dashed ellipse shows the osculating (instantaneous) Keplerian orbit.
Figure-8: Three equal masses trace a figure-eight path—a famous exact solution discovered by Chenciner & Montgomery (2000).
Controls: Space to play/pause, R to reset, mouse wheel to zoom, drag to pan. Center on any body with the Center buttons.