1. Sodium and Potassium Signatures of Volcanic Satellites Orbiting Close-in Gas Giant Exoplanets
- Author
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Christoph Mordasini, Diana Gamborino, Carl Schmidt, Brice-Olivier Demory, Robert E. Johnson, Chenliang Huang, Apurva Oza, Emmanuel Lellouch, Prabal Saxena, Nicolas Thomas, Aurélien Wyttenbach, Nicholas M. Schneider, Arielle Moullet, David Dubois, Andrea Gebek, Universität Bern [Bern], University of Virginia [Charlottesville], New York University [New York] (NYU), NYU System (NYU), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Boston University [Boston] (BU), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], University of Nevada [Las Vegas] (WGU Nevada), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Leiden University, NASA Goddard Space Flight Center (GSFC), NASA Ames Research Center Cooperative for Research in Earth Science in Technology (ARC-CREST), NASA Ames Research Center (ARC), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich)
- Subjects
Solar System ,010504 meteorology & atmospheric sciences ,530 Physics ,Gas giant ,FOS: Physical sciences ,Astrophysics ,Orbital decay ,7. Clean energy ,01 natural sciences ,Jupiter ,Atmosphere ,0103 physical sciences ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences ,Physics ,[PHYS]Physics [physics] ,Earth and Planetary Astrophysics (astro-ph.EP) ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,520 Astronomy ,Astronomy and Astrophysics ,620 Engineering ,Exoplanet ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Physics::Space Physics ,Astrophysics::Earth and Planetary Astrophysics ,Equivalent width ,Astrophysics - Earth and Planetary Astrophysics ,Exosphere - Abstract
Extrasolar satellites are generally too small to be detected by nominal searches. By analogy to the most active body in the Solar System, Io, we describe how sodium (Na I) and potassium (K I) $\textit{gas}$ could be a signature of the geological activity venting from an otherwise hidden exo-Io. Analyzing $\sim$ a dozen close-in gas giants hosting robust alkaline detections, we show that an Io-sized satellite can be stable against orbital decay below a planetary tidal $\mathcal{Q}_p \lesssim 10^{11}$. This tidal energy is focused into the satellite driving a $\sim 10^{5 \pm 2}$ higher mass loss rate than Io's supply to Jupiter's Na exosphere, based on simple atmospheric loss estimates. The remarkable consequence is that several exo-Io column densities are on average $\textit{more than sufficient}$ to provide the $\sim$ 10$^{10 \pm 1}$ Na cm$^{-2}$ required by the equivalent width of exoplanet transmission spectra. Furthermore, the benchmark observations of both Jupiter's extended ($\sim 1000$ R$_J$) Na exosphere and Jupiter's atmosphere in transmission spectroscopy yield similar Na column densities that are purely exogenic in nature. As a proof of concept, we fit the "high-altitude" Na at WASP 49-b with an ionization-limited cloud similar to the observed Na profile about Io. Moving forward, we strongly encourage time-dependent ingress and egress monitoring along with spectroscopic searches for other volcanic volatiles., Comment: 23 pages, 5 figures, accepted to ApJ
- Published
- 2019