Effect of UV radiation on the spectral fingerprints of earth-like planets orbiting m stars

Journal article

We model the atmospheres and spectra of Earth-like planets orbiting the entire grid of M dwarfs for active and inactive stellar models with T_eff = 2300 K to T_eff = 3800 K and for six observed MUSCLES M dwarfs with UV radiation data. We set the Earth-like planets at the 1 AU equivalent distance and show spectra from the visible to IR (0.4–20 μm) to compare detectability of features in different wavelength ranges with the James Webb Space Telescope and other future ground- and spaced-based missions to characterize exo-Earths. We focus on the effect of UV activity levels on detectable atmospheric features that indicate habitability on Earth, namely, H₂O, O₃, CH₄, N₂O, and CH₃Cl. To observe signatures of life—O₂/O₃ in combination with reducing species like CH₄—we find that early and active M dwarfs are the best targets of the M star grid for future telescopes. The O₂ spectral feature at 0.76 μm is increasingly difficult to detect in reflected light of later M dwarfs owing to low stellar flux in that wavelength region. N₂O, another biosignature detectable in the IR, builds up to observable concentrations in our planetary models around M dwarfs with low UV flux. CH₃Cl could become detectable, depending on the depth of the overlapping N₂O feature. We present a spectral database of Earth-like planets around cool stars for directly imaged planets as a framework for interpreting future light curves, direct imaging, and secondary eclipse measurements of the atmospheres of terrestrial planets in the habitable zone to design and assess future telescope capabilities.

Authors: Rugheimer, S; Kaltenegger, L; Segura, A; Linsky, J; Mohanty, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Astrophysical Journal
• Volume: 809
• Issue: 1
• Pages: 57-57
• Publication date: 2015-08-10
• Acceptance date: 2015-06-10
• DOI: 10.1088/0004-637x/809/1/57
• EISSN: 1538-4357
• ISSN: 0004-637X
• Keywords: SBTMR; planets and satellites: terrestrial planets; planets and satellites: atmospheres; stars:low-mass; astrobiology