ESA Chooses Cheops as Next Exoplanet Hunter

The European Space Agency (ESA) announced today that the CHaracterizing ExOPlanets Satellite (Cheops) will be the first small satellite in ESA’s Science Programme.  The announcement comes just two days after European astronomers revealed they had discovered an exoplanet orbiting Alpha Centauri, the nearest star to our Sun, using a ground-based telescope.

Scheduled for launch in 2017, Cheops will join other ground- and space-based instruments searching for and studying planets orbiting other stars in the universe — exoplanets.  In particular it will be looking for “super-Earths,” planets more massive than Earth up to the size of Neptune.   The project is a partnership between ESA and Switzerland.  The satellite will be placed into an 800-kilometer sun-synchronous Earth orbit.

Cheops will look for planets using the transit approach where it will detect the dimming of a star as a planet passes in front of it.  It will focus on nearby bright stars already known to have planets and measure the radius of those planets.  If a planet’s mass is known, its density then can be calculated thereby revealing other characteristics.

The small satellite category of ESA space science missions is new and attracted 26 proposals when it was announced last spring.  The satellites are supposed to be low cost and developed quickly.  ESA refers to this as a “possible new class” of ESA missions suggesting that its success or failure in meeting those criteria could determine the future of the category.

The astrophysics community is quite excited about exoplanets these days.  Data from NASA’s Kepler space telescope has confirmed the existence of 77 planets around other stars in our galaxy, with another 2,321 candidates for which additional data is required before confirmation.  The European discovery regarding Alpha Centauri earlier this week was made using a telescope at the European Southern Observatory in Chile.