Abstract
The tidal evolution of planets orbiting brown dwarfs (BDs) presents an
interesting case study because BDs' terrestrial planet forming region is
located extremely close-in. In fact, the habitable zones of BDs range
from roughly 0.001 to 0.03 AU [1] and for the lowestmass BDs are located
interior to the Roche limit. In contrast with stars, BDs spin up as they
age. Thus, the corotation distance moves inward. We study the tidal
evolution of planets around BDs using a standard tidal model and test
the effect of numerous parameters such as the initial semi-major axis
and eccentricity, the rotation period of the BD, the masses of both star
and planet, and their tidal dissipation factor. We find that the most
important parameter is the initial orbital distance with respect to the
corotation distance. We find that all planets that form at or beyond the
corotation distance and with initial eccentricities smaller than ∼ 0.1
and are repelled from the star. Some planets initially interior to
corotation can survive if their inward tidal evolution is slower than
the BD's spin evolution, although most initially close-in planets fall
onto the BD. As the luminosity of BDs decreases dramatically on Gyr
timescales [2], the habitable zone moves inward in time. A close-in
planetary orbit can pass through the habitable zone simply due to the
BD's cooling. For higher-mass BDs, planets can survive in the habitable
zone for Gyr timescales.
Original language | English |
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Pages (from-to) | 588 |
Journal | EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France |
Publication status | Published - 2011 |
Externally published | Yes |