Detectability of Atmospheric Features Of Earth-like Planets In The Habitable Zone Around M Dwarfs

Planets orbiitng an M Class Star

We investigate the detectability of atmospheric spectral features of Earth-like planets in the habitable zone (HZ) around M dwarfs with the future James Webb Space Telescope (JWST).

We use a coupled 1D climate-chemistry-model to simulate the influence of a range of observed and modelled M-dwarf spectra on Earth-like planets. The simulated atmospheres served as input for the calculation of the transmission spectra of the hypothetical planets, using a line-by-line spectral radiative transfer model. To investigate the spectroscopic detectability of absorption bands with JWST we further developed a signal-to-noise ratio (S/N) model and applied it to our transmission spectra. High abundances of CH4 and H2O in the atmosphere of Earth-like planets around mid to late M dwarfs increase the detectability of the corresponding spectral features compared to early M-dwarf planets.

Increased temperatures in the middle atmosphere of mid- to late-type M-dwarf planets expand the atmosphere and further increase the detectability of absorption bands. To detect CH4, H2O, and CO2 in the atmosphere of an Earth-like planet around a mid to late M dwarf observing only one transit with JWST could be enough up to a distance of 4 pc and less than ten transits up to a distance of 10 pc. As a consequence of saturation limits of JWST and less pronounced absorption bands, the detection of spectral features of hypothetical Earth-like planets around most early M dwarfs would require more than ten transits.

We identify 276 existing M dwarfs (including GJ 1132, TRAPPIST-1, GJ 1214, and LHS 1140) around which atmospheric absorption features of hypothetical Earth-like planets could be detected by co-adding just a few transits. We show that using transmission spectroscopy, JWST could provide enough precision to be able to partly characterise the atmosphere of Earth-like TESS planets around mid to late M dwarfs.

F. Wunderlich, M. Godolt, J.L. Grenfell, S. St├Ądt, A.M.S. Smith, S. Gebauer, F. Schreier, P. Hedelt, H. Rauer
(Submitted on 7 May 2019)

Comments: 18 pages, 10 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: A&A 624, A49 (2019)
DOI: 10.1051/0004-6361/201834504
Cite as: arXiv:1905.02560 [astro-ph.EP] (or arXiv:1905.02560v1 [astro-ph.EP] for this version)
Submission history
From: Fabian Wunderlich
[v1] Tue, 7 May 2019 13:39:13 UTC (1,084 KB)
https://arxiv.org/abs/1905.02560
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