Decaying Orbit of the Hot Jupiter WASP-12b: Confirmation with TESS Observations

Theory suggests that the orbits of some close-in giant planets should decay due to tidal interactions with their host stars. To date, WASP-12b is the only hot Jupiter reported to have a decaying orbit, at a rate of 29$\pm$2 msec year${}^{-1}$. We analyzed data from NASA’s Transiting Exoplanet Survey Satellite (TESS) to verify that WASP-12b’s orbit is indeed changing. We find that the TESS transit and occultation data are consistent with a decaying orbit with an updated period of 1.091420090$\pm$0.000000041 days and a decay rate of 32.53$\pm$1.62 msec year${}^{-1}$. We find an orbital decay timescale of $\tau$ = P/$\mathrm{\mid }\dot{P}\mathrm{\mid }$ = 2.90$\pm$0.14 Myr. If the observed decay results from tidal dissipation, the modified tidal quality factor is Q’${}_{\star }$ = 1.39$\pm$0.15 $\times {10}^5$, which falls at the lower end of values derived for binary star systems and hot Jupiters. Our result highlights the power of space-based photometry for investigating the orbital evolution of short-period exoplanets.