ESA’s M4 mission, positioned at Lagrange point L2, the Ariel spacecraft will probe the atmospheres of some 1,000 exoplanets for at least 4 years, during their transit phases in front of their host stars, to study their chemical composition. Reliable ephemerides are essential to optimize the mission. With this in mind, a project with a strong societal impact has been launched, involving both professional and amateur astronomers: the ExoClock project, created and coordinated at University College London by Anastasia Kokori and Angelos Tsiaras: “ExoClock is a project to monitor transiting exoplanets in order to keep their ephemerides up-todate. Everyone with some basic equipment, including a telescope and a CCD camera, can participate in the effort of monitoring the planets’ host stars.”
The French branch of Exoclock brings together amateurs and professionals in the field of astronomy, and the colloquium is intended to provide a specific opportunity for a community concerned with the observation of transit ephemerides of exoplanets to get together for practical work.