Greek 'exo' (outside) + 'planetes' (wanderer) — a planet orbiting a star beyond our solar system.
A planet that orbits a star outside our solar system; an extrasolar planet.
From Greek 'exō' (outside, external) + 'planētēs' (wanderer, planet), from 'planan' (to wander). The prefix 'exo-' (from Greek 'exō,' outside, from 'ex,' out of) was added to 'planet' to denote planets beyond our solar system. The first confirmed exoplanets were detected in 1992 (orbiting a pulsar) and 1995 (orbiting a Sun-like star, 51 Pegasi). The word
As of 2026, over 5,700 exoplanets have been confirmed. The prefix 'exo-' (outside) comes from the same Greek root that gives us 'exotic' (foreign, from outside) and 'exodus' (a going out). An exoplanet is thus an 'outside wanderer' — a wandering star's companion discovered beyond our solar neighborhood.