Journal Article

Spin–orbit coupling for tidally evolving super-Earths

A. Rodríguez, N. Callegari, T. A. Michtchenko and H. Hussmann

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 427, issue 3, pages 2239-2250
Published in print December 2012 | ISSN: 0035-8711
Published online December 2012 | e-ISSN: 1365-2966 | DOI:
Spin–orbit coupling for tidally evolving super-Earths

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We investigate the spin behaviour of close-in rocky planets and the implications for their orbital evolution. Considering that the planet rotation evolves under simultaneous actions of the torque due to the equatorial deformation and the tidal torque, both raised by the central star, we analyse the possibility of temporary captures in spin–orbit resonances.

The results of the numerical simulations of the exact equations of motions indicate that, whenever the planet rotation is trapped in a resonant motion, the orbital decay and the eccentricity damping are faster than the ones in which the rotation follows the so-called pseudo-synchronization. Analytical results obtained through the averaged equations of the spin–orbit problem show a good agreement with the numerical simulations.

We apply the analysis to the cases of the recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The simulated dynamical history of these systems indicates the possibility of capture in several spin–orbit resonances; particularly, GJ 3634 b and 55 Cnc e can currently evolve under a non-synchronous resonant motion for suitable values of the parameters. Moreover, 55 Cnc e may avoid a chaotic rotation behaviour by evolving towards synchronization through successive temporary resonant trappings.

Keywords: celestial mechanics; planets and satellites: general

Journal Article.  9383 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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