Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory
Monthly Notices of the Royal Astronomical Society, vol. 524, pp. 5477–5485
Abstract
ABSTRACT NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds ), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can reveal ocean glint, rainbows, and other phenomena caused by scattering by clouds or atmospheric gas. Direct imaging missions are optimized for planets near quadrature, but HabWorlds ’ coronagraph may obscure the phase angles where such optical features are strongest. The range of accessible phase angles for a given exoplanet will depend on the planet’s orbital inclination and/or the coronagraph’s inner working angle (IWA). We use a recently created catalog relevant to HabWorlds of 164 stars to estimate the number of exo-Earths that could be searched for ocean glint, rainbows, and polarization effects due to Rayleigh scattering. We find that the polarimetric Rayleigh scattering peak is accessible in most of the exo-Earth planetary systems. The rainbow due to water clouds at phase angles of ∼20○ − 60○ would be accessible with HabWorlds for a planet with an Earth equivalent instellation in ∼46 systems, while the ocean glint signature at phase angles of ∼130○ − 170○ would be accessible in ∼16 systems, assuming an IWA = 62 mas (3λ/D). Improving the IWA = 41 mas (2λ/D) increases accessibility to rainbows and glints by factors of approximately 2 and 3, respectively. By observing these scattering features, HabWorlds could detect a surface ocean and water cycle, key indicators of habitability.
Authors 44
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Sophia R. Vaughan corresponding
Affiliation as printed
Astrophysics, Department of Physics, University of Oxford , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH , UK
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ETH Zurich · Max Planck Institute for Intelligent Systems · Institute for Particle Physics and Astrophysics
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ETH Zurich, Institute for Particle Physics and Astrophysics , Wolfgang-Pauli-Str 27, 8092 Zurich , Switzerland
Max Planck Institute for Intelligent Systems , Max-Planck-Ring 4, 72076 Tübingen , Germany
ETH Zurich, Institute for Particle Physics & Astrophysics, Wolfgang-Pauli-Str. 27, 8092 Zurich, Switzerland
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University of California, Riverside · University of Central Florida · University of Washington · National Aeronautics and Space Administration
Affiliation as printed
Department of Earth and Planetary Sciences, University of California Riverside , 900 University Ave., Riverside, CA 92521 , USA
NASA Nexus for Exoplanet System Science, Terrestrial Polarization Team , 4111 Libra Drive, University of Central Florida, Orlando, FL 32826 , USA
NASA Nexus for Exoplanet System Science, Virtual Planetary Laboratory Team , Bldg. 3910, 15th Ave NE, University of Washington, Seattle, WA 98195 , USA
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Affiliation as printed
Centre for Exoplanet Research, School of Physics and Astronomy, University of Leicester , University Road, Leicester, LE1 7RH , UK
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Affiliation as printed
Department of Earth and Planetary Sciences and Department of Physics, McGill University , 3600 rue University, Montréal, QC, H3A 2T8 , Canada
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Leiden University · Leiden Observatory · Space Research Organisation Netherlands
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
SRON Netherlands Institute for Space Research , Niels Bohrweg 4, 2333 CA , Leiden, the Netherlands
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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Centre National de la Recherche Scientifique · Université Paris Cité · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
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LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université , Université de Paris , 5 Place Jules Janssen, 92195 Meudon, France
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University of California, Santa Barbara
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Department of Physics, University of California , Broida Hall , Santa Barbara, CA 93106, USA
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Royal Netherlands Meteorological Institute · Delft University of Technology
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Department of Geoscience and Remote Sensing, Delft University of Technology , Stevinweg 1, 2628 CN , Delft, the Netherlands
Royal Netherlands Meteorological Institute (KNMI) , Utrechtseweg 297, 3731 GA , de Bilt, the Netherlands
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Delft University of Technology
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Delft University of Technology , Kluyverweg 1, 2629 HS Delft, the Netherlands
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STAR Institute, Université de Liége , Allée du six Août 19c, 4000 Liége, Belgium
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Centre National de la Recherche Scientifique · Aix-Marseille Université
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Aix Marseille Université, CNRS, CNES, LAM , 38 rue Frédéric Joliot-Curie, 13388 Cedex 13, Marseille, France
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Centre National de la Recherche Scientifique · Université Paris Cité · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
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LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris , 5 Place Jules Janssen, 92195 Meudon, France
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Affiliation as printed
NASA Ames Research Center , Bldg. 245, Moffett Field, USA
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
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Université Grenoble Alpes, CNRS, IPAG , 25 Av. des Martyrs, 38000 Grenoble, France
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Affiliation as printed
Astrophysics, Department of Physics, University of Oxford , Denys Wilkinson Building, Keble Road , Oxford OX1 3RH, UK
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ETH Zurich · Institute for Particle Physics and Astrophysics
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ETH Zurich, Institute for Particle Physics and Astrophysics , Wolfgang-Pauli-Str 27, 8092 Zurich, Switzerland
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
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Université Grenoble Alpes, CNRS, IPAG , 25 Av. des Martyrs, 38000 Grenoble, France
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Centre National de la Recherche Scientifique · Aix-Marseille Université
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Aix Marseille Université, CNRS, CNES, LAM , 38 rue Frédéric Joliot-Curie, 13388 Cedex 13, Marseille, France
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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California Institute of Technology
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Department of Astronomy, California Institute of Technology , 1200 East California Boulevard , Pasadena, CA, 91125, USA
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NASA Ames Research Center , Bldg. 245, Moffett Field, USA
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University of California, Santa Cruz
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Department of Astronomy and Astrophysics, University of California , 1156 High Street , Santa Cruz, CA 95064, USA
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Steward Observatory, University of Arizona , 933 North Cherry Avenue , Tucson, AZ 85719, USA
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Centre National de la Recherche Scientifique · Université Paris Cité · Université Paris Sciences et Lettres · Université Paris-Saclay · Observatoire de Paris · Office National d'Études et de Recherches Aérospatiales · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique · Département Traitement de l’Information et Systèmes · Département Optique et Techniques Associées
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DOTA, ONERA , 29 avenue de la Division Leclerc, 92322 Châtillon, France
DTIS, ONERA, Université Paris Saclay , 6 Chemin de la Vauve aux Granges, 91123 Palaiseau, France
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris , 5 Place Jules Janssen, 92195 Meudon, France
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University of Arizona · Astrobiology Center · National Astronomical Observatory of Japan
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Astrobiology Center , 2 Chome-21-1 , Osawa, Mitaka, Tokyo 181-8588, Japan
College of Optical Sciences, University of Arizona , 1630 E University Blvd , Tucson, AZ 85721, USA
Steward Observatory, University of Arizona , 933 North Cherry Avenue , Tucson, AZ 85719, USA
Subaru Telescope, NAOJ , 650 N Aohoku Pl, HI 96720 , USA
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Steward Observatory, University of Arizona , 933 North Cherry Avenue , Tucson, AZ 85719, USA
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Université Paris-Saclay · Office National d'Études et de Recherches Aérospatiales · Département Traitement de l’Information et Systèmes
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DTIS, ONERA, Université Paris Saclay , 6 Chemin de la Vauve aux Granges, 91123 Palaiseau, France
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
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Université Grenoble Alpes, CNRS, IPAG , 25 Av. des Martyrs, 38000 Grenoble, France
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Goddard Space Flight Center · University of Maryland, Baltimore County
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NASA Goddard Space Flight Center , 8800 Greenbelt Rd , Greenbelt, MD 20771, USA
University of Maryland Baltimore County , 1000 Hilltop Cir , Baltimore, MD 21250, USA
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Leiden University · Leiden Observatory · Delft University of Technology
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Faculty of Aerospace Engineering, TU Delft , Building 62, Kluyverweg 1, 2629 HS Delft, the Netherlands
Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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STAR Institute, Université de Liége , Allée du six Août 19c, 4000 Liége, Belgium
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Herzberg Institute of Astrophysics · National Research Council Canada
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National Research Council Canada, Herzberg Astronomy and Astrophysics Research Center , 5071 W Saanich Rd , Victoria, B.C., Canada
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European Space Agency · European Space Research and Technology Centre
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European Space Agency, ESTEC , Keplerlaan 1, 2200 AG Noordwijk, the Netherlands
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Centre National de la Recherche Scientifique · Université Paris Cité · Université Paris Sciences et Lettres · Observatoire de Paris · Sorbonne Université · Laboratoire d’études spatiales et d’instrumentation en astrophysique
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LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris , 5 Place Jules Janssen, 92195 Meudon, France
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
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Université Grenoble Alpes, CNRS, IPAG , 25 Av. des Martyrs, 38000 Grenoble, France
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
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Université Grenoble Alpes, CNRS, IPAG , 25 Av. des Martyrs, 38000 Grenoble, France
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Centre National de la Recherche Scientifique · Université Côte d'Azur · Lagrange Laboratory · Observatoire de la Côte d’Azur
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Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange , Boulevard de l'Observatoire , Nice, France
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Space Telescope Science Institute
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Space Telescope Science Institute , 3700 San Martin Drive , Baltimore, MD 21218, USA
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Space Telescope Science Institute
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Space Telescope Science Institute , 3700 San Martin Drive , Baltimore, MD 21218, USA
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Leiden University · Leiden Observatory
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Leiden Observatory, Leiden University , P.O. Box 9513, 2300 RA Leiden, the Netherlands
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