The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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Artist impression of the different types of exoplanets and their host stars that might be studied by ESA’s Characterising Exoplanet Satellite, Cheops.
Cheops will make precise measurements of planets known to be orbiting around nearby bright stars. The mission makes use of the technique of ‘ultra-high-precision transit photometry’ to measure very precisely the sizes of exoplanets. The size of the dip in the light due to the exoplanet transit is known as the ‘depth’ of the transit, and relates directly to the size of the planet relative to the star: a large planet will block a larger fraction of the light from the star than would a small one.
It will focus particularly on stars with Earth- to Neptune-sized planets. By determining the size of the planet, and combining this with known measurements of the planets’ masses, Cheops will allow the density of the planet to be estimated, and therefore enable a first step towards characterising the nature of these planets – from lava worlds to rocky Earth-like planets, to gas planets or even ocean worlds.