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Exoplanet

An exoplanet is a planet that is located outside our Solar System.

While there is currently no formal agreement on what exactly defines an exoplanet, the word is used to indicate planet-sized bodies that are located beyond our Solar System. By convention, exoplanets have sufficient mass to maintain a roughly spherical shape, but not so much mass that nuclear fusion is triggered in them (as is the case for stars). They might orbit one star, a pair of stars, or multiple stars — or not orbit a star at all. The categorisation of exoplanets is also not formalised, but certain categories are typically used, including Hot Jupiters, Super Earths and Mini Neptunes. The discovery of the first exoplanet was only confirmed in 1992, when two exoplants were discovered orbiting a pulsar.

Webb is already revolutionising the study of exoplanets — in particular by examining their atmospheres. The chemical makeup of a planet’s atmosphere leaves a unique fingerprint on the starlight that passes through it, which Webb can study.

You can learn more about how Webb studies exoplanets in this video.