Exoplanets & Exomoons

L 98-59: a Benchmark System of Small Planets for Future Atmospheric Characterization

By Keith Cowing
June 3, 2021
Filed under
L 98-59: a Benchmark System of Small Planets for Future Atmospheric Characterization
Representation of the cosmic shoreline (Zahnle & Catling 2017), shown as a solid line. Additional dashed and dotted lines assume XUV flux 16 and 256 times higher than solar, respectively. Solar system bodies are shown as red circles, and exoplanets as small blue dots. The L 98- 59 and TRAPPIST-1 planets are indicated by green triangle and cyan squares, respectively.

L 98-59 is an M3V dwarf star that hosts three small (R < 1.6 Earth radii) planets. The host star is bright (K = 7.1) and nearby (10.6 pc), making the system a prime target for follow-up characterization with the Hubble Space Telescope (HST) and the upcoming James Webb Space Telescope (JWST). Herein, we use simulated transmission spectroscopy to evaluate the detectability of spectral features with HST and JWST assuming diverse atmospheric scenarios (e.g., atmospheres dominated by H2, H2O, CO2, or O2). We find that H2O and CH4 present in a low mean-molecular weight atmosphere could be detected with HST in 1 transit for the two outermost planets, while H2O in a clear steam atmosphere could be detected in 6 transits or fewer with HST for all three planets. We predict that observations using JWST/NIRISS would be capable of detecting a clear steam atmosphere in 1 transit for each planet, and H2O absorption in a hazy steam atmosphere in 2 transits or less. In a clear, desiccated atmosphere, O2 absorption may be detectable for all three planets with NIRISS. If the L 98-59 planets possess a clear, Venus-like atmosphere, NIRSpec could detect CO2 within 26 transits for each planet, but the presence of H2SO4 clouds would significantly suppress CO2 absorption. The L 98-59 system is an excellent laboratory for comparative planetary studies of transiting multiplanet systems, and observations of the system via HST and JWST would present a unique opportunity to test the accuracy of the models presented in this study. Daria Pidhorodetska, Sarah E. Moran, Edward W. Schwieterman, Thomas Barclay, Thomas J. Fauchez, Nikole K. Lewis, Elisa V. Quintana, Geronimo L. Villanueva, Shawn D. Domagal-Goldman, Joshua E. Schlieder, Emily A. Gilbert, Stephen R. Kane, Veselin B. Kostov Comments: Submitted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2106.00685 [astro-ph.EP] (or arXiv:2106.00685v1 [astro-ph.EP] for this version)
Submission history
From: Daria Pidhorodetska
[v1] Tue, 1 Jun 2021 18:00:02 UTC (11,541 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻