Abstract

With the recent direct detection of the giant planet HR 8799 e by VLTI /GRAVITY, optical interferometry has become a new arrow in the quiver of exoplanet observers. By taking advantage of the angular-resolution offered by 100+ meter baselines, optical interferometers can separate a dim exoplanet from the overwhelming residual starlight, leading to accurate measurements of the astrometric position (up to 10 uas) and high signal-to-noise spectroscopic data.

Starting from the basic physics of long-baseline interferometry, I will go through a detailed description of VLTI /GRAVITY and its peculiar “dual-field” mode, in order to explain how exoplanets can be observed with this instrument. Beware: there will be some equations and a lot of technical details. But if you want to know how dual-field long-baseline interferometry actually works, here is your chance!

And if you can bear with this rather technical part, then I will show the results obtained on the second target we observed, beta Pictoris b, and discuss what we can learn about this object from the new GRAVITY K -band spectrum