Detection of exoplanets: exploiting each property of light

Up to now and probably for still a long time, the only support of information used to detect exoplanets has been the analysis of light, either visible or infrared. In the vast majority of cases it is the light from a star and not the light from the planet itself which is used, because the huge contrast in brightness between the star and a planet orbiting it as well as the extremely short angular distance between them makes direct imaging a real challenge. It is then a subtle effect detected on the starlight that in general indicates the planet’s presence and provides information on some of its characteristics: mass, radius, distance to the star, temperature, etc. As an introduction to the different contributions appearing in this volume, this article proposes a kind of brief review of the various methods imagined by astronomers to exploit one of the properties of the light to succeed in detecting and characterizing exoplanets. We’ll show that even direct detection became a reality and contributes to the more than 5000 exoplanets detected today.