Kepler-22b

Kepler-22b is an exoplanet about 600 light-years away, orbiting the Sun-like star Kepler-22. It was the first planet discovered in a star’s habitable zone by NASA’s Kepler mission.

Kepler space telescope: NASA space observatory that searched for exoplanets by measuring periodic dips in starlight. Kepler detected the recurring dimming that revealed Kepler-22b.
Planetary transit: The passage of a planet across the disk of its host star as seen by an observer. Each observed passage produced a small, repeatable dip in Kepler-22’s brightness.
Earth analog: A planet similar to Earth in properties such as size, composition, temperature, or orbit. Kepler-22b’s habitable-zone orbit alone does not make it an Earth analog.
Kepler mission: NASA’s space telescope mission that monitored stars for transiting exoplanets from 2009 to 2018. The mission’s survey produced the observations used to confirm Kepler-22b.
Transit method: An exoplanet detection technique that measures a star’s dimming when a planet crosses its face. Kepler-22b was identified through repeated transits across its star.
Transit depth: The fractional decrease in a star’s observed brightness during a planetary transit. The depth of Kepler-22b’s transits helps determine its radius relative to its star.
Super-Earth: An exoplanet more massive than Earth but lighter than the Solar System’s ice giants, with no single agreed composition implied. Its estimated radius places Kepler-22b among planets often discussed as super-Earths or sub-Neptunes.
Kepler-22b discovery: The 2011 announcement identifying a transiting planet in the habitable zone of Kepler-22. The discovery established the milestone associated with this planet.
Habitable zone: The range of distances from a star where a planet could maintain liquid water on its surface under suitable conditions. Kepler-22b’s orbit was the first found within this zone around a Sun-like star.
Orbital period: The time a body takes to complete one orbit around another body. The spacing between Kepler-22b’s transits reveals its roughly 290-day orbit.

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Kepler-452bRelated: It was an earlier Kepler habitable-zone candidate, providing context for Kepler-452b’s 2015 announcement.