Hot Jupiters, gas giants orbiting close to their host stars, provide key opportunities to explore planetary interiors and dynamics due to their extreme environments. WASP-43b, a well-studied "ultra-hot Jupiter," orbits its host star in less than a day, making it an ideal candidate for investigating tidal decay and orbital precession. These phenomena, driven by gravitational interactions, offer insights into the internal structure and history of such planets.

Methods: Observing WASP-43b

To unravel WASP-43b's dynamics, researchers combined multiple datasets, including observations from HARPS (High Accuracy Radial velocity Planet Searcher) and the James Webb Space Telescope (JWST). This study marks the first integration of JWST's full-phase light curve data with transit and radial velocity measurements, supplemented by additional unpublished radial velocity datasets. Advanced modeling techniques were applied to account for tidal decay, apsidal motion, and long-term system acceleration.

Findings: Tidal Decay and Orbital Precession Detected

The team identified a tidal decay rate of approximately 1.99 milliseconds per year, alongside an apsidal precession rate of 0.1727 degrees per day. Remarkably, this is the first confirmed simultaneous detection of these two phenomena in an exoplanetary system. The findings suggest significant gravitational interactions between WASP-43b and its host star. However, the exact cause of the observed precession remains unresolved, as common explanations—like misaligned stellar rotation axes or non-synchronous planetary rotation—are insufficient.

Discussion: Planetary Love Numbers and Rotation

WASP-43b's eccentric orbit, despite its proximity to the star, hints at a young or dynamically unique system. The absence of a second planetary body or distant companion, based on extensive modeling and Gaia data, further complicates explanations for the detected precession. The study highlights the importance of the Love number, a measure of how a planet's mass is distributed, but WASP-43b’s specific value remains elusive due to observational limitations.

Conclusion: Unveiling the Dynamics of WASP-43b

This comprehensive study sheds light on the dynamic interactions shaping WASP-43b's orbit, providing a foundation for future research. As observations expand with advanced instruments like JWST, scientists hope to clarify the processes driving tidal decay and apsidal motion, offering broader implications for the evolution of exoplanetary systems.

Source: Bernabò