THE HIGH ECCENTRICITY OF THE PLANET ORBITING 16-CYGNI-B

We consider the high eccentricity, 0.63, of the newly discovered plane t orbiting 16 Cyg B, using the fact that the parent star is part of a wide binary. We show that the high eccentricity of the planet could be the result of tidal forces exerted on 16 Cyg B and its planet by 16 C yg A, the distant companion in the system. By following numerically st ellar triple systems with parameters similar to those of 16 Cyg, we ha ve established that the orbital eccentricity of the planet could have gone through strong modulation, with an amplitude of 0.8 or even large r, with typical timescale of tens of millions of years. The amplitude of the modulation of the orbital eccentricity strongly depends on the relative inclination between the plane of motion of the planet and tha t of the wide binary 16 Cyg AB. To account for the present eccentricit y of the planet, we have to assume that the angle between the two plan es of motion is large, at least 60 degrees. We argue that this assumpt ion is not unreasonable for wide binaries like 16 Cyg AB.