Transits: Corot, Kepler, TESS, PLATO, ASTEP

Observing exoplanet transits requires extremely high photometric precision and is therefore an ideal candidate for space missions.

Corot was the first space telescope designed for searching for exoplanets using the transit method. This CNES and Observatoire de Paris mission, combined the study of star seismology with the search for transiting exoplanets. It was launched in 2006 and was to discover several tens of planets, including CoRoT-7 b which, with a radius of 1.7 Earth radii and a mass of 7.3 Earth masses, is the first confirmed rocky exoplanet, with a density and composition similar to those of Earth.

Kepler is NASA’s first planet-hunter satellite^?. It was launched in 2009 and scanned 145,000 stars in a field of 100 square degrees in the constellation of Cygnus and went on to identify more than 2,600 confirmed exoplanets. It shows that planetary systems are extremely varied, often comprise several planets, and that the most numerous exoplanets are super-Earths with a mass between that of Earth and Neptune.

TESS : n 2018, NASA launched the Transiting Exoplanet Survey Satellite^?. The main aim of TESS is to find exoplanets close to Earth and it has detected several tens of telluric planets in the habitable zone (HZ) of bright and nearby stars. To do this, it sweeps virtually the entire sky and, in particular, looks at Sun-type yellow stars and orange ones. It can detect planets with an orbital period^? around their star of about ten days. Once a planet is detected, TESS hands over to a more powerful instrument such as the JWST to study its atmosphere.

PLATO (PLAnetary Transits and Oscillations of stars) is a space telescope project developed by the European Space Agency (ESA), one of the main aims of which is to discover and characterise Earth-type exoplanets around nearby stars. This mission must determine to what extent our Solar System and the Earth are an atypical grouping or whether such groupings are widespread throughout the Universe.