Search for signatures of HD209458 b's atmosphere

Abstract

A technique to obtain information on the composition of atmospheres of extra-solar planets is to observe the light of the star through the planetary atmosphere during transit phases of the planet. Atmospheric atoms and molecules will then produce absorption features which may be detected by high-resolution spectroscopic observations. We observed HD209458 during two transit phases of its planet using the Utrecht Echelle Spectrograph at the 4m William-Herschel telescope ath the Roque de los Muchachos observatory on La Palma, covering a wavelength range of about 4040-6840 Å. We present a first analysis of the obserations, including upper limits on the sodium absorption depths caused by the planet's atmosphere.