Abstract

After centuries of speculations, the last twenty years have seen the discovery of hundreds of planets orbiting other stars. This ‘expolanet revolution’ has led to a real breakthrough in the history of science. It has revealed that most stars host planets, and the billions of terrestrial planets potentially able to host life exist in our Milky Way alone. To go one step further towards an answer to the tantalizing question “Are we alone?” we now have to detect habitable planets amenable to the search for life signatures in their atmosphere with our current instrumentation. In this respect, the most promising targets are the coolest and smallest objects in the solar neighbourhood, including not only very-low-mass stars but also ‘brown dwarfs’, i.e. faint substellar objects too low in mass to sustain the core nuclear reactions that define a star. An Earth-sized planet eclipsing periodically one of the nearest of these small celestial objects could be detected by a telescope of relatively modest size, and the atmospheric traces of life on its surface could be scrutinized by one of the giant telescopes currently in preparation. Just funded by the European Research Council, the project SPECULOOS aims to seize this first opportunity to detect life outside our solar system. I will present here its instrumental concept, its goals, and its status.