In the year of the 20th anniversary of the discovery of the first extrasolar planet we can count more than 1800 companions found with different techniques. The majority of them are indirect methods that infer the presence of an orbiting body by observing the parent star (radial velocity, transits, astrometry). In this work we explore the technique that permits to directly observe planets and retrieve their spectra, under the conditions that they are bright and far enough from their host star.
Direct imaging is a new technique became possible thanks to a new generation of extreme adaptive optics instruments mounted on 8m class telescopes. On the Very Large Telescope two instruments dedicated to the research for exoplanets with direct imaging are now operative: NACO and SPHERE.
This thesis will describe the development and results of SPHERE from its predecessor NACO to its integration in laboratory and the final on sky results.
Chapter 1 gives a presentation of the exoplanet research, the formation mechanisms, and the characterization of planet atmospheres. Chapter 2 gives a general frame of the two instruments used for the results presented in this thesis: NACO and SPHERE. In Chapter 3 I describe an example of a false positive in the direct imaging technique, found during the survey NACO-Large Program. This work have been published in Zurlo et al. 2013. In Chapter 4 I present the performance of SPHERE, in particular of the subsystems IRDIS and IFS, deeply tested in the laboratory before the shipping to Paranal. This work has been published in Zurlo et al. 2014. Chapter 5 presents a work done to find special targets for the NIRSUR survey, these object are radial velocity long period planets which are observable with SPHERE. In Chapter 6 I present one of the first on sky result, the observations and analysis of the multi-planetary system HR\,8799. In Chapter 7 I give the conclusions and future prospects
