The study of planets outside our solar system.
An exoplanet is a planet orbiting a star other than the Sun. The first confirmed detection was only in 1992, orbiting a pulsar, and in 1995 around a normal star. Early detections were by terrestrial telescope. The large number of recent detections has been made by the NASA Kepler telescope, launched in 2009. Apart from being fascinating in itself, the significance of exoplanets is that they form in the early years of a star’s lifecycle. Observing large numbers, at different stages of a star’s life, tells us about planet formation. The light from an exoplanet can be used to infer the chemical composition of the planet and atmosphere.