An exoplanet is any planet which is not in our solar system. The prefix “exo” originates from Greek and translates into “outside”. Although exoplanets were thought to exist in ancient times, it was not until 1992 when the first confirmed discovery of an exoplanet, was made by Wolszczan & Frail (1992). They discovered two planets which orbited a 6.2 ms pulsar ~500 pc away by studying timing variations using the biggest telescope in the world, the 305 m Arecibo radio telescope.
The subsequent discoveries of exoplanets, notably the first detection of an exoplanet around a sun like star (Mayor & Queloz 1995), the first detection of a transiting planet (Charbonneau et al. 2000) and an exoplanet atmosphere (Charbonneau et al. 2002), used a range of techniques which will be described in more detail below.
Thanks to a number of exoplanet surveys aimed at detecting exoplanets, and the subsequent follow-up studies aimed at characterising them, the first few steps to understanding these new worlds have been made. With exoplanets known to outnumber stars (Cassan et al. 2012), and with new powerful telescopes and instruments on their way (e.g., JWST, E-ELT) the future of exoplanet research has an exciting future ahead.