Broadband transmission spectroscopy of HD209458b with ESPRESSO

ESPRESSO detected the transmission spectrum of #HD209458b, finding evidence for the presence of TiO and Sodium (one of them, or both). These exciting results appear in a new paper led by Nuno Santos (see it on the arxiv).

By observing the Rossiter-McLaughlin (RM) effect at different wavelengths, which provides a chromatic measurement of the planet radius, we can determine the extent of the planet’s atmosphere and build a broadband transmission spectrum.

The transmission spectrum looks different depending on the chemical elements that are present in the planet’s atmosphere. We found evidence for TiO and Na, or perhaps both elements together.

The spectrum of HD209458b also suggests there may exist extra absorbers and tentative hints of spectral variability. More observations or more precise model atmospheres are needed to conclude on this.

ESPRESSO’s result is comparable to the one previously obtained with @NASAHubble . But this new detection was achieved from the ground in a completely independent way and using a different approach.

The precision of ESPRESSO in combination with the chromatic RM technique opens the possibility to study in detail the atmospheres of other exoplanets.