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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The first planet discovered using the transit method was HD 209458 b in 1999. Interestingly, it was also the first planet whose atmosphere was studied. When a planet transits its star, part of the starlight is absorbed by particles in the atmosphere. The NASA/ESA Hubble Space Telescope became the first satellite to ever measure the composition of an atmosphere of an exoplanet. HD 209458 b is a popular target for space missions, being also revisited by ESA’s Cheops mission in 2020. Using data from this visit, scientists discovered that the planet has a dark outlook and no clouds in its atmosphere.