Formation, tidal evolution, and habitability of the Kepler-186 system
- Univ. Bordeaux, Laboratoire d'Astrophysique de Bordeaux, UMR 5804, F-33270 Floirac (France)
- Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Rutherfordstrasse 2, D-12489 Berlin (Germany)
- SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States)
- NASA Ames Research Center, Moffett Field, CA 94035 (United States)
The Kepler-186 system consists of five planets orbiting an early M dwarf. The planets have physical radii of 1.0-1.50 R {sub ⊕} and orbital periods of 4-130 days. The 1.1 R {sub ⊕} Kepler-186f with a period of 130 days is of particular interest. Its insolation of roughly 0.32 S {sub ⊕} places it within the surface liquid water habitable zone (HZ). We present a multifaceted study of the Kepler-186 system, using two sets of parameters which are consistent with the data and also self-consistent. First, we show that the distribution of planet masses can be roughly reproduced if the planets were accreted from a high surface density disk presumably sculpted by an earlier phase of migration. However, our simulations predict the existence of one to two undetected planets between planets e and f. Next, we present a dynamical analysis of the system including the effect of tides. The timescale for tidal evolution is short enough that the four inner planets must have small obliquities and near-synchronous rotation rates. The tidal evolution of Kepler-186f is slow enough that its current spin state depends on a combination of its initial spin state, its dissipation rate, and the stellar age. Finally, we study the habitability of Kepler-186f with a one-dimensional climate model. The planet's surface temperature can be raised above 273 K with 0.5-5 bars of CO{sub 2}, depending on the amount of N{sub 2} present. Kepler-186f represents a case study of an Earth-sized planet in the cooler regions of the HZ of a cool star.
- OSTI ID:
- 22365065
- Journal Information:
- Astrophysical Journal, Vol. 793, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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