The Plato project (PLAnetary Transits and Oscillations of stars) aims to discover Earth-like planets orbiting nearby Sun-like stars.
Plato was selected by ESA in 2014 and is scheduled to be launched in 2026 towards the L2 Lagrangian point, 1.5 million km from Earth. The satellite will monitor tens of thousands of bright stars, looking for tiny and periodic brightness variations which would indicate a planet is passing in front of its stars. This method, called transit monitoring, was successfully implemented by the Kepler and CoRoT space telescopes.
The difference is that Plato won’t stop at detecting planets around nearby stars; it will also determine the planets’ characteristics with unprecedented accuracy. This is a crucial condition in order to verify the planets’ nature and determine that it is indeed a rocky planet. Discovering this type of planet in Sun-like stars’ habitable zone (the distance from the star at which liquid water can be found on the planet) would be a major step in our search for extra-terrestrial life.
Artist’s impression of exoplanet HD 188753 Ab’s three stars (one of which has set), as seen from a hypothetical satellite hidden behind the planet ©NASA/JPL-Caltech
To achieve those goals, once it has detected a suitable planet, Plato will analyse its host star’s seismic signals. Using these vibrations, Plato will accurately determine the stars’ mass, radius and age, in order to determine the nature of the planets it discovers and understand exoplanetary systems’ diversity, formation, and evolution. And finally, since Plato will observe bright stars, the planets’ characteristics, including their atmospheres, will be analysed in detail using telescopes on Earth to search for any indication of life.
CNES funds the French contribution to Plato and will soon name a Programme Manager to supervise the satellite’s development. It will most likely provide technical support to the CEA and to LAM. French teams will also play a major role in the mission’s ground segment to catalogue exoplanetary systems.