58 research outputs found
Chaotic dynamics of the planet in HD 196885 AB
Depending on the planetary orbit around the host star(s), a planet could
orbit either one or both stars in a binary system as S-type or P-type,
respectively. We have analysed the dynamics of the S-type planetary system in
HD 196885 AB with an emphasis on a planet with a higher orbital inclination
relative to the binary plane. The mean exponential growth factor of nearby
orbits (MEGNO) maps are used as an indicator to determine regions of
periodicity and chaos for the various choices of the planet's semimajor axis,
eccentricity and inclination with respect to the previously determined
observational uncertainties. We have quantitatively mapped out the chaotic and
quasi-periodic regions of the system's phase space which indicate a likely
regime of the planet's inclination. In addition, we inspect the resonant angle
to determine whether alternation between libration and circulation occurs as a
consequence of Kozai oscillations, a probable mechanism that can drive the
planetary orbit to a very large inclination. Also, we demonstrate the possible
higher mass limit of the planet and improve upon the current dynamical model
based on our analysis.Comment: 10 pages, 9 figures (Accepted for publication at MNRAS
Long-Term Stability of Planets in the Alpha Centauri System
The alpha Centauri system is billions of years old, so planets are only expected to be found in regions where their orbits are long-lived. We evaluate the extent of the regions within the alpha Centauri AB star system where small planets are able to orbit for billion-year timescales, and we map the positions in the sky plane where planets on stable orbits about either stellar component may appear. We confirm the qualitative results of Wiegert & Holman (Astron. J. 113, 1445, 1997) regarding the approximate size of the regions of stable orbits of a single planet, which are larger for retrograde orbits relative to the binary than for pro-grade orbits. Additionally, we find that mean motion resonances with the binary orbit leave an imprint on the limits of orbital stability, and the effects of the Lidov-Kozai mechanism are also readily apparent. Overall, orbits of a single planet in the habitable zones near the plane of the binary are stable, whereas high-inclination orbits are short-lived. However, even well within regions where single planets are stable, multiple planet systems must be significantly more widely-spaced than they need to be around an isolated star in order to be long-lived
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