Water vapour detection in HD 189733b with CARMENES

We have detected water vapour in the exoplanet hot Jupiter HD 189733b in multiple bands in the near-IR (Alonso-Floriano, F.J, Sánchez-López A., et al. 2019).
This represents the first detection of a molecule in an exo-atmosphere with the CARMENES instrument using the high-dispersion spectroscopy technique. Water vapour detection from the ground is very challenging because the our atmosphere (telluric) absorption. However, the detection is possible thanks to the Doppler shift between the Earth atmospheric water vapour absoprtion lines and the weak signal coming from the exoplanet atmosphere. For that detection we use the CCF (cross-correlation technique) which accummulates the very weak  signals of thousand of absorption lines. The novelty of our work was the detection at several bands. This might open the possibility for studying also the clouds and haze in these exo-atmospheres because of their different absoprtion in the different bands.