Characterising the composition of a hot Jupiter

Transiting hot-Jupiters provide an excellent opportunity to detect and characterize exoplanetary atmospheres. To be able to perform a wide scale comparative exoplanetology however, we have to observe targets which are too faint for the Hubble Space Telescope. To do this, we used the GTC telescope (above image) together with unique tunable filters capable of precision narrowband photometry at specific wavelengths to study transiting hot-Jupiters. This technique coupled with the use of the worlds largest optical telescope allowed us to obtain high precision light curves well suited for detecting sodium and potassium in the atmospheres of hot-Jupiters.

Through my analysis of several exoplanets using tunable filters, I was amongst the first to detected potassium in the atmosphere of an exoplanet (HAT-P-1 b, Wilson et al 2015). The strong presence of potassium is likely caused by the large atmospheric scale height, which in turn can be explained by a higher temperature in the upper atmosphere. A lower mean molecular mass caused by the dissociation of molecular hydrogen into atomic hydrogen by the extreme ultraviolet flux from the host star may also partly explain the amplitude of the detection.