Astronomy Tea Talk

There are now a number of catastrophically disintegrating transiting rocky planets, characterized by comet-like tails and tenuous tori. The physics fueling their spectral and photometric behavior closely parallels that of tidally heated volcanic exoplanets and exomoons embedded in magnetospheres. I present 3-D kinetic simulations of neutral sodium and sulfur dioxide gases limited by photoionization at several volcanic systems and show that time-series data near eclipse exhibits gradual rock disintegration in infrared photometry (JWST/NIRCam) for 55 Cancri. For the far more elusive volcanic exomoon candidates, I argue that high-resolution spectroscopy is needed to unambiguously differentiate the Doppler velocity of a third body with respect to its primary and host star. Due to the unique geometry of transmission spectroscopy and the preferred blueshift vector from stellar radiation pressure, the detection of a significant Doppler redshift of an alkali metal (as at Io and Europa) requires a third body. This appears to be the case for WASP-49 A b I, orbiting near the Roche limit (~8 h) of its hot Saturn host. In contrast, low-resolution JWST/MIRI observations of WASP-39 b I provide only dynamical bounds (5.8–15.3 h). Given that even Europa sustains a sputtered sodium exosphere, future large-aperture and space-based instrumentation designed for habitable worlds may consider evaporating exomoons as viable volatile sources. 
To join on Zoom: https://caltech.zoom.us/j/88139532758