Normalized total flux and normalized linearly polarized flux phase curves of a cloudy planet with a wavy sea surface and an Earth-like atmosphere in an edge-on orbit (adapted from Trees & Stam 2019). The sea surface wind speed (Cox & Munk 1954), which determines the wave height, is 7 m/s and the clouds are composed of spherical water droplets. The cloud coverage is 0.5, the cloud pattern is mottled, but the glow is always cloudless. The flux is normalized so that the total (i.e. unpolarized + polarized) flux is equal to the planet’s geometrical albedo at phase angle 𝛼 = 0°. The lower panel shows the scattering angle ranges for Glory, Rainbow, Rayleigh Scattering, and Sea Glow. Note that the actual curve features partially overlap. Glory illustrations are taken from Zakovryashin & Prigarin (2020).All other illustrations are from unsplash.com [1, 2, 3]. This figure is best viewed in color. — astro-ph.EP
NASA is working on plans for the Habitable World Observatory (HabWorlds). This is a coronagraphic space mission to detect rocky planets within the habitable zone and establish their habitability.
Surface liquid water is central to the definition of a planet’s habitability. Photometric and polarization phase curves of star light reflected by exoplanets can reveal sea glows, rainbows, and other phenomena caused by scattering by clouds and atmospheric gases. Direct-imaging missions are optimized for planets near quadrature, but the HabWorlds coronagraph can obscure the phase angles where such optical features are strongest.
The range of phase angles accessible for a particular exoplanet depends on the planet’s orbital inclination and/or the coronagraph’s inner working angle (IWA). We use his HabWorlds-related recently produced catalog of 164 stars to estimate the number of extraterrestrial planets for which polarization effects due to ocean glow, rainbows, and Rayleigh scattering can be searched. We find that polarized Rayleigh scattering peaks are accessible in most of the extraterrestrial planetary systems.
Water cloud rainbows at ~20−60∘ phase angles are accessible in the HabWorlds of planets with Earth-equivalent constellations in the ~46 system, while oceanic glow features at ~130–170∘ phase angles. is accessible. In about 16 systems, assuming IWA=62 masses (3λ/D). Improving IWA=41 mas (2λ/D) increases the accessibility to rainbows and sparkles by a factor of approximately 2 and 3, respectively. By observing these scattering features, HabWorlds was able to detect surface ocean and water cycles, which are important indicators of habitability.
Sophia R. Vaughan (1), Timothy D. Gebhardt (2, 3), Kimberly Vott (4, 5, 6), Sarah L. Casewell (7), Nicholas B. Cowan (8), David S. Dollman (9) Matthew Kenworthy (9), Johan Mazoyer (11), Maxwell A. Miller-Blancher (12), Victor J.H. Trees (13, 14), Daphne・ M. Stam (15), Olivier Abcil (16), Lisa Altinier (17), Pierre Boardes (11), Ruslan Belikov (18), Alexis Bideau (19), Jane L. Barkby (1) ), Markus J. Bonse (3), Bernhard Brundle (9), Alexis Carlotti (19), Elodie Choque (17), Dirk Van Damme (9), Nyati Desai (20), Kevin Fogerty (18), J. Fowler (21), Kyle van Gocombe (22), Jan Gutierrez (11, 23, 24), Olivier Guillon (22, 25, 26, 27), Sebastian Y. Hafert (22), Olivier Herscowisi-Shiller (23), Adrian Hour (19), Rosa Juanola Palamon (28, 29), Evangelia Kreissioti (9, 30), Lorenzo Koenig (16), Mayike van Kooten (31), Mariya Krasteva (32), Iva Lazinha (11), Rico Landmann (9), Lucy Lebouleur (19), David Mouillet (19), Mamadou Ndiaye (33) ), Emiel H. Poe (34), Laurent Puejo (34), Frans Snick (9) ((1) Department of Physics, University of Oxford, Astrophysics, (2) Max Planck Institute for Intelligent Systems, (3) ETH Zurich Institute for Particle Physics and Astrophysics, (4) Department of Earth and Planetary Sciences, University of California, Riverside, (5) NASA Exoplanet Systems Science Nexus, Virtual Planet Experiment Team, (6) NASA Exoplanet Systems Science Nexus, Earth Polarization Team, (7) Center for Exoplanet Studies, Department of Physics and Astronomy, University of Leicester, (8) Department of Earth and Planetary Sciences and Department of Physics, McGill University, (9) Leiden Observatory, University of Leiden, (10) ) SRON Netherlands Space Institute , (11) LESIA, Paris Observatory, PSL University, CNRS, Sorbonne University, University of Paris, (12) Department of Physics, University of California, Santa Barbara, (13) Department of Earth Sciences, Remote Sensing, Delft University of Technology, (14) Royal Netherlands Meteorological Institute (KNMI), (15) Delft University of Technology, (16) University of Liège STAR Institute, (17) Aix-Marseille University, CNRS, CNES, LAM, (18) NASA Ames Research Center, (19) Grenoble Alpes University , CNRS, IPAG, (20) Department of Astronomy, California Institute of Technology, (21) Department of Astronomy and Astrophysics, University of California, Santa Cruz, (22) University of Arizona Steward Observatory, (23) University of Paris-Saclay DTIS, ONERA, (24) DOTA, ONERA, (25) NAOJ Subaru Telescope, (26) University of Arizona, Department of Optical Science, (27) Astrobiology Center, Tokyo, (28) NASA Goddard Space Flight Center, (29) University of Maryland, Baltimore County, (30) Delft University of Technology, Aerospace Engineering Department, (31) National Research Council of Canada, Hertzberg Research Center for Astronomy and Astrophysics, (32) European Space Agency, ESTEC, (33) Cote d’Azur University, Côte d’Azur Observatory, CNRS , Lagrange Institute, (34) Space Telescope Science Institute)
Comment: MNRAS approved, 9 pages, 8 figures, 3 tables
Subject: Earth and Planetary Astrophysics (astro-ph.EP)
Quote: arXiv:2307.15137 [astro-ph.EP] (or arXiv:2307.15137v1 [astro-ph.EP] for this version)
Related DOIs:
https://doi.org/10.1093/mnras/stad2127
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Birthplace: Sophia Vaughan
[v1] Thursday, July 27, 2023 18:17:31 UTC (1,801 KB)
https://arxiv.org/abs/2307.15137
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