exoplanet

American  

[ek-soh-plan-it] / ˈɛk soʊˌplæn ɪt /

noun

Astronomy.

1. a planet that revolves around a star other than the sun.

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exoplanet British  

/ ˈɛksəʊˌplænɪt /

noun

1. a planet that orbits a star in a solar system other than that of Earth

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exoplanet Scientific  

/ ĕk′sō-plăn′ĭt /

1. See extrasolar planet

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Other Word Forms

• exoplanetary adjective

Etymology

Origin of exoplanet

First recorded in 1970–75; exo- + planet

Explanation

An exoplanet is a planet that revolves around a different sun than ours. Sometimes a pizza takes so long to be delivered, you think it must be coming from one of the furthest known exoplanets! In the 1970s, when space science was taking off, the word exoplanet was invented by attaching the combining form exo-, meaning "outside," to the word planet. That English form exo- comes from the Greek, also meaning "outside," and is used in this case because the planet is outside our solar system. Exoskeleton is another word that uses this combining form, and refers to the hard supporting structure found on the outside of certain animals such as insects and crabs.

Example Sentences

This is because the most common method of studying exoplanet atmospheres requires the planet to pass in front of its star from Earth's perspective.

From Science Daily • Apr. 22, 2026

A newly studied exoplanet, Kepler-51d, is wrapped in an unusually dense layer of haze that may be hiding both what it is made of and how it formed.

From Science Daily • Mar. 18, 2026

Among other discoveries, the telescope produced the first ever image of an exoplanet -- a planet outside our solar system -- in 2004.

From Barron's • Feb. 2, 2026

Scientists using NASA's James Webb Space Telescope have identified a previously unknown kind of exoplanet, one whose atmosphere defies current ideas about how planets are supposed to form.

From Science Daily • Jan. 1, 2026

Large clouds of dust can closely mimic the appearance of an exoplanet by reflecting starlight, potentially misleading astronomers.

From Science Daily • Jan. 1, 2026