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Rocky super-Earth interiors - Structure and internal dynamics of CoRoT-7b and Kepler-10b

Wagner, F.W. und Tosi, N. und Sohl, F. und Rauer, H. und Spohn, T. (2012) Rocky super-Earth interiors - Structure and internal dynamics of CoRoT-7b and Kepler-10b. Astronomy and Astrophysics, 541 (A103), Seiten 1-13. EDP Sciences. DOI: 10.1051/0004-6361/201118441

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Offizielle URL: http://dx.doi.org/10.1051/0004-6361/201118441


Aims. We present interior structure models of the recently discovered exoplanets CoRoT-7b and Kepler-10b addressing their bulk compositions, present thermal states, and internal dynamics. We investigate how mantle convection patterns are influenced by the depth-dependence of thermodynamic parameters (e.g., thermal expansivity and conductivity) caused by the extended pressure and temperature ranges within rocky super-Earths. Methods. To model the interior of rocky exoplanets, we construct a four-layer structural model solving the mass and energy balance equations in conjunction with a generalized Rydberg equation of state providing the radial density distribution within each layer. The present thermal state is calculated according to a modified mixing-length approach for highly viscous fluids. Furthermore, the obtained internal structure is used to carry out two-dimensional convection simulations to visualize the mantle convection pattern within massive exoplanets such as CoRoT-7b and Kepler-10b. Results. Both CoRoT-7b and Kepler-10b most likely have large iron cores and a bulk composition similar to that of Mercury. For a planetary radius of Rp = (1.58 �± 0.10) Râ��, a revised total mass of Mp = (7.42 �± 1.21) Mâ��, and the existence of a third planet in the CoRoT-7 planetary system, calculations suggest that an iron core of 64 wt-% and a silicate mantle of 36 wt-% is produced owing to the relatively high average compressed density of ��avg = (10.4 �± 1.8) g cm-3. Kepler-10bâ��s planetary radius and total mass yield an iron core of 59.5 wt-%, which complements the silicate mantle of 40.5 wt-%. An enhanced radiogenic heating rate owing to CoRoT-7bâ��s young age (1.2â��2.3 Gyr) raises the radial distribution of temperature by only a few hundred Kelvin, but reduces the viscosity by an order of magnitude. The planform of mantle convection is found to be strongly modified for depth-dependent material properties, with hot plumes rising across the whole mantle and cold slabs, which stagnate in the mid-mantle because of the loss of buoyancy. Conclusions. We use a new model approach to determine the detailed interior structures and present thermal states of CoRoT-7b and Kepler-10b. Both planets are found to be enriched in iron. The results imply that modest radiogenic heating does not play a significant role in determining the internal structure of rocky exoplanets. The depth-dependence of thermodynamic properties, however, strongly influences the mantle convection patterns within exoplanets such as CoRoT-7b and Kepler-10b. This may have a significant effect on the thermal evolution and magnetic field generation of close-in super-Earths.

Titel:Rocky super-Earth interiors - Structure and internal dynamics of CoRoT-7b and Kepler-10b
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iD
Wagner, F.W.frank.wagner@dlr.deNICHT SPEZIFIZIERT
Tosi, N.nicola.tosi@dlr.deNICHT SPEZIFIZIERT
Sohl, F.frank.sohl@dlr.deNICHT SPEZIFIZIERT
Rauer, H.heike.rauer@dlr.deNICHT SPEZIFIZIERT
Spohn, T.tilman.spohn@dlr.deNICHT SPEZIFIZIERT
Datum:10 Mai 2012
Erschienen in:Astronomy and Astrophysics
Referierte Publikation:Ja
In Open Access:Nein
In ISI Web of Science:Ja
DOI :10.1051/0004-6361/201118441
Seitenbereich:Seiten 1-13
Verlag:EDP Sciences
Stichwörter:planets and satellites: interiors / planets and satellites: composition / planets and satellites: individual: CoRoT-7b / planets and satellites: individual: Kepler-10b
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Weltraum (alt)
HGF - Programmthema:W EW - Erforschung des Weltraums
DLR - Schwerpunkt:Weltraum
DLR - Forschungsgebiet:W EW - Erforschung des Weltraums
DLR - Teilgebiet (Projekt, Vorhaben):W - Projekt COROT Beteiligung (alt)
Standort: Berlin-Adlershof
Institute & Einrichtungen:Institut für Planetenforschung > Planetenphysik
Institut für Planetenforschung > Extrasolare Planeten und Atmosphären
Hinterlegt von: Sohl, Frank
Hinterlegt am:30 Mai 2012 08:24
Letzte Änderung:08 Mär 2018 18:54

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