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Murray-Clay, Ruth

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Murray-Clay

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Ruth

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Murray-Clay, Ruth

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2009 - 200912010 - 20151

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    C/o and Snowline Locations in Protoplanetary Disks: The Effect of Radial Drift and Viscous Gas Accretion
    (IOP Publishing, 2015) Piso, Ana-Maria Adriana; Oberg, Karin; Birnstiel, Tilman; Murray-Clay, Ruth
    The C/O ratio is a defining feature of both gas giant atmospheric and protoplanetary disk chemistry. In disks, the C/O ratio is regulated by the presence of snowlines of major volatiles at different distances from the central star. We explore the effect of radial drift of solids and viscous gas accretion onto the central star on the snowline locations of the main C and O carriers in a protoplanetary disk, H2O, CO2 and CO, and their consequences for the C/O ratio in gas and dust throughout the disk. We determine the snowline locations for a range of fixed initial particle sizes and disk types. For our fiducial disk model, we find that grains with sizes ∼0.5 cm . s . 7 m for an irradiated disk, and ∼0.001 cm . s . 7 m for an evolving and viscous disk, desorb at a size-dependent location in the disk, which is independent of the particle’s initial position. The snowline radius decreases for larger particles, up to sizes of ∼7 m. Compared to a static disk, we find that radial drift and gas accretion in a viscous disk move the H2O snowline inwards by up to 40 %, the CO2 snowline by up to 60 %, and the CO snowline by up to 50 %. We thus determine an inner limit on the snowline locations when radial drift and gas accretion are accounted for.
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    A Super-Earth Transiting a Nearby Low-Mass Star
    (Nature Publishing Group, 2009) Charbonneau, David; Berta, Zachory; Irwin, Jonathan; Burke, Christopher J.; Nutzman, Philip; Buchhave, Lars A.; Lovis, Christophe; Bonfils, Xavier; Latham, David; Udry, Stéphane; Murray-Clay, Ruth; Holman, Matthew; Falco, Emilio E.; Winn, Joshua N.; Queloz, Didier; Pepe, Francesco; Mayor, Michel; Delfosse, Xavier; Forveille, Thierry
    A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9–10 times the Earth’s mass (Mcircle plus), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b , but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55Mcircle plus and a radius 2.68 times Earth’s radius (Rcircle plus), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen–helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.