Resonant Frequencies Reveal Evaporating Exomoons at Several Alkaline Exoplanet Systems

Moons are very much alive. Jupiter’s tidally-heated moons Io and Europa, offer a synergy of [cryo]volcanic volatiles to study in-situ and remotely via spectroscopy. Io and Europa’s combination of fiery and icy volatiles when driven into Jupiter’s magnetosphere, enable us to study the general problem of how active and irradiated bodies release heavy atoms into space and consequently help us predict signatures of their activity. When the volatiles escape, they can absorb or emit at specific resonance frequencies, enabling estimates of the total quantity of the gas. Remarking on recent discoveries of metals at extrasolar gas giants, I shall demonstrate that these metals are not inconsistent with a volcanically-active exomoon, or exo-Io. The need for a third body is best shown due to an anomalous signature of an alkali metal, atomic sodium (Na I) at the planet WASP-49b. High-resolution spectroscopy has revealed extreme broadening of the Na I line cores, which cannot be explained by a canonical planetary atmosphere in hydrostatic equilibrium at present. Furthermore, the inferred equivalent width from observations corresponds to a column density of ~10^10.7 Na cm^-2 consistent with the expected escape from a tidally-heated exo-Io, yet too large by roughly three orders of magnitude for an exoplanetary wind (~10^(7+/-3) Na cm^-2).  Lastly, I will discuss ongoing observations and studies of HD189733b and several alkaline exoplanet systems, whose spectra are consistent with an exo-Io or its consequential exoring, yet difficult to explain using a planet alone. Due to their small size,  exomoons have evaded astronomers for decades. This novel spectral technique  may be promising for future discoveries beyond exoplanets.