The orbital motion, absolute mass and high-altitude winds of exoplanet HD 209458b

Abstract

If the orbital velocity of an extrasolar planet could be determined, the masses of both the planet and its host star could be calculated using Newton's law of gravity. Here, high-dispersion ground-based spectroscopy of a transit of the extrasolar planet HD 209458b is reported. This allowed the radial component of the planet's orbital velocity to be calculated, and thus the masses of star and planet. Moreover, a strong wind flowing from the irradiated dayside to the non-irradiated nightside of the planet is suggested.