astro-ph.EP

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# Title: Formation, tidal evolution and habitability of the Kepler-186 system

Abstract: The Kepler-186 system consists of five planets orbiting an early-M dwarf. The planets have physical radii of 1.0-1.50 R$_\oplus$ and orbital periods of 4 to 130 days. The $1.1~$R$_\oplus$ Kepler-186f with a period of 130 days is of particular interest. Its insolation of roughly $0.32~S_\odot$places it within the liquid water habitable zone. We present a multi-faceted study of the Kepler-186 system. First, we show that the distribution of planet masses can be roughly reproduced if the planets accreted from a high-surface density disk presumably sculpted by an earlier phase of migration. However, our simulations predict the existence of 1-2 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. Tidal evolution of Kepler-186f is slow enough that its current spin state depends on a combination of its dissipation rate and the stellar age. Finally, we study the habitability of Kepler-186f with a 1-D climate model. The planet's surface temperature can be raised above 273 K with 0.5-5 bars of CO$_2$, depending on the amount of N$_2$ present. Kepler-186f represents a case study of an Earth-sized planet in the cooler regions of the habitable zone of a cool star.
 Comments: Paper accepted in ApJ Subjects: Earth and Planetary Astrophysics (astro-ph.EP) DOI: 10.1088/0004-637X/793/1/3 Cite as: arXiv:1404.4368 [astro-ph.EP] (or arXiv:1404.4368v2 [astro-ph.EP] for this version)

## Submission history

From: Emeline Bolmont [view email]
[v1] Wed, 16 Apr 2014 20:00:11 GMT (2144kb,D)
[v2] Fri, 5 Sep 2014 09:51:12 GMT (2154kb,D)
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