The Kepler Space Telescope made some of the most exciting discoveries in astronomy. Launched in 2009, the telescope observed 13 million stars until 2018, when it was de-activated.
During that time, Kepler discovered over 2600 planets orbiting other stars. Some were entirely unlike anything in our Solar System, forcing astronomers to invent two new classes of planet. One or two of Kepler’s discoveries even orbit in the habitable zone of their parent star, albeit around red dwarf stars that are rather different from our Sun. This was hugely exciting because this temperate region in which liquid water can exist has conditions thought crucial for the existence of life.
