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Burrows A Guillot T Hubbard WB Marley MS Saumon D Lunine JI Sudarsky D 《The Astrophysical journal》2000,534(1):L97-L100
The recent discovery that the close-in extrasolar giant planet HD 209458b transits its star has provided a first-of-its-kind measurement of the planet's radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet tau Bootis b. Including the effects of stellar irradiation, we estimate the general behavior of radius/age trajectories for such planets and interpret the large measured radii of HD 209458b and tau Boo b in that context. We find that HD 209458b must be a hydrogen-rich gas giant. Furthermore, the large radius of a close-in gas giant is not due to the thermal expansion of its atmosphere but to the high residual entropy that remains throughout its bulk by dint of its early proximity to a luminous primary. The large stellar flux does not inflate the planet but retards its otherwise inexorable contraction from a more extended configuration at birth. This implies either that such a planet was formed near its current orbital distance or that it migrated in from larger distances (>/=0.5 AU), no later than a few times 107 yr of birth. 相似文献
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J. Schneider A. Boccaletti D. Mawet P. Baudoz J.-L. Beuzit R. Doyon M. Marley D. Stam G. Tinetti W. Traub J. Trauger A. Aylward J. Y-K. Cho C.-U. Keller S. Udry 《Experimental Astronomy》2009,23(1):357-377
The Super-Earth Explorer is an Off-Axis Space Telescope (SEE-COAST) designed for high contrast imaging. Its scientific objective is to make the physico-chemical characterization of exoplanets possibly down to 2 Earth radii. For that purpose it will analyze the spectral and polarimetric properties of the parent starlight reflected by the planets, in the wavelength range 400–1,250 nm. 相似文献
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Models of Uranus and Neptune are computed based on the assumption that these planets consist of three layers: a rock core, an ice shell, and an atmosphere. Uranus models require that the ice shell have a density some 10% lower than the canonical density for an ice mixture. Two Neptune models are found, one with the canonical density in the ice shell, and one with a density 20% lower. The implications of these models are discussed. 相似文献
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Stephens Denise C. Marley Mark Gelino C. R. Lunine Jonathon I. 《Earth, Moon, and Planets》1998,81(1):105-106
Earth, Moon, and Planets - 相似文献
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J. J. Fortney M. S. Marley O. Hubickyj P. Bodenheimer J. J. Lissauer 《Astronomische Nachrichten》2005,326(10):925-929
Here we show preliminary calculations of the cooling and contraction of a 2 MJ planet. These calculations, which are being extended to 1–10 MJ, differ from other published “cooling tracks” in that they include a core accretion‐gas capture formation scenario, the leading theory for the formation of gas giant planets.We find that the initial post‐accretionary intrinsic luminosity of the planet is ∼3 times less than previously published models which use arbitrary initial conditions. These differences last a few tens of millions of years. Young giant planets are intrinsically fainter than has been previously appreciated. We also discuss how uncertainties in atmospheric chemistry and the duration of the formation time of giant planets lead to challenges in deriving planetary physical properties from comparison with tabulated model values. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Application of a radiative-convective equilibrium model to the thermal structure of Uranus' atmosphere evaluates the role of hazes in the planet's stratospheric energy budget and places a lower limit on the internal energy flux. The model is constrained by Voyager and post-Voyager observations of the vertical aerosol and radiative active gas profiles. Our baseline model generally reproduces the observed tropospheric and stratospheric temperature profile. However, as in past studies, the model stratosphere from about 10(-3) to 10(-1) bar is too cold. We find that the observed stratospheric hazes do not warm this region appreciably and that any postulated hazes capable of warming the stratosphere sufficiently are inconsistent with Voyager and ground-based constraints. We explore the roles played by the stratospheric methane abundance, the H2 pressure-induced opacity, photochemical hazes, and C2H2, and C2H6 in controlling the temperature structure in this region. Assuming a vertical methane abundance profile consistent with that found by the Voyager UVS occultation observations, the model upper stratosphere, from 10 to 100 microbar, is also too cold. Radiation in the 7.8-micrometers band from a small abundance of hot methane in the lower thermosphere absorbed in this region can warm the atmosphere and bring models into closer agreement with observations. Finally, we find that internal heat fluxes < or approximately 60 erg cm-2 sec-1 are inconsistent with the observed tropospheric temperature profile. 相似文献
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Matthew Coggon Caryl Ann Becerra Klaus Nüsslein Karen Miller Richard Yuretich Sarina J. Ergas 《Geochimica et cosmochimica acta》2012
Biological reduction of iron-sulfate minerals, such as jarosite, has the potential to contribute to the natural attenuation of acid mine drainage (AMD) sites. Previous studies of AMD attenuation at Davis Mine, an abandoned pyrite mine in Rowe Massachusetts, provided evidence of iron and sulfate reduction by indigenous bacteria. Jarosite is a large component of the sediment at Davis Mine and may play a role in AMD attenuation. In this study, microcosms were constructed with groundwater and sediment from Davis Mine and amended with glycerol, nitrogen and phosphorus (GNP) and naturally formed natrojarosite. Over time, higher total iron, sulfate, pH and sodium concentrations and lower oxidation–reduction potentials were observed in microcosms amended with GNP and jarosite, compared with unamended microcosms and killed controls. Geochemical modeling predicted jarosite precipitation under microcosm conditions, suggesting that abiotic processes were unlikely contributors to jarosite dissolution. SEM imaging at the jarosite surface showed microbial attachment. Microbial community composition analysis revealed a shift to higher populations of Clostridia, which are known to reduce both iron and sulfate. The results show that jarosite may be utilized as an electron acceptor by iron and/or sulfate reducing bacteria at Davis Mine and its presence may aid in the attenuation of AMD. 相似文献
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The Induced Gravitational Collapse (IGC) paradigm points to a binary origin for the longduration gamma-ray burst (GRBs) associated with supernovae (SN). In this one, a carbon-oxygen core (COcore) explodes in a Type Ib/c SN in presence of a close neutron star (NS) companion. The SN triggers a hypercritical accretion into the NS and depending on the initial binary parameters, two outcomes are possible givimg place to two family of long GRBs: binary-driven hypernova (BdHNe), where the NS reaches its critical mass, and collapses to a black hole (BH), emitting a GRB; and x-ray flashes (XRFs) where the hypercritical accretion onto the NS is not sufficient to induce its gravitational collapse. We perform 3-dimensional (3D) numerical simulations of the IGC paradigm with the smoothed particle hydrodynamics (SPH) technique. We determine whether the star gravitational collapse is possible and assess if the binary holds gravitationally bound or it becomes unbound by the SN explosion. 相似文献