Exoplanet Orbital Dynamics
A hidden companion cannot explain WASP-12b's rapid fall
Accepted research rules out the planet needed to sustain one tidal-decay mechanism, leaving the famous inspiral unexplained.
Briefed September 11, 2026 · Aliens in the Clouds
Accepted Research · Cause Still Unresolved
WASP-12b's orbital period is shrinking faster than standard equilibrium or dynamical tides in a main-sequence star appear able to explain. One proposed solution held that a nearby low-mass planet could maintain WASP-12b's tilt, allowing strong obliquity tides inside the hot Jupiter to keep draining orbital energy instead of damping themselves away.
Caleb Lammers, Yubo Su, and Joshua Winn reworked the angular-momentum accounting and found that the companion would need at least about 65 Earth masses—far above the roughly ten Earth masses previously proposed. Their radial-velocity analysis excludes a companion of that kind within three astronomical units at 95 percent confidence, with allowed signals below about 14 meters per second. The accepted paper eliminates this specific mechanism; it does not identify the actual cause of the decay.
Why it matters
Ruling out an attractive explanation is real progress. The remaining mismatch can sharpen models of stellar interiors, planetary tides, and the final evolution of ultra-close giant planets.
What the source establishes
Verified manuscript accepted by Astrophysical Journal Letters. The companion-driven obliquity mechanism is disfavored; the cause of WASP-12b's orbital decay remains unresolved.
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