Kepler-186f

Kepler-186f is an approximately Earth-size exoplanet orbiting the red dwarf Kepler-186 every 130 days. Discovered in 2014, it was the first Earth-size planet found in the habitable zone of another star.

Kepler-186: Kepler-186 is a cool M-dwarf star about 500 light-years away in the constellation Cygnus. This is the star whose light Kepler-186f periodically blocks.
Kepler space telescope: NASA’s Kepler space telescope monitored stellar brightness to find planets through transits. Kepler gathered the brightness data that revealed the planet’s repeated transits.
Kepler-186e: Kepler-186e is an exoplanet orbiting the same red dwarf star as Kepler-186f, closer to the star. It is another member of the system, receiving more stellar energy than Kepler-186f.
Atmospheric characterization: Atmospheric characterization determines a planet’s atmospheric composition and properties from observations of its light. No detailed atmospheric composition is known for Kepler-186f.
Habitable zone: The habitable zone is the range of distances where a planet could maintain liquid water on its surface under suitable conditions. Kepler-186f receives starlight consistent with this zone, but its actual surface conditions are unknown.
Transit photometry: Transit photometry measures the brightness change when a planet passes in front of its star. The depth and timing of these dips underpin estimates of Kepler-186f’s radius and period.
Kepler-186d: Kepler-186d is an exoplanet in the Kepler-186 system, orbiting between planets c and e. Its place in the same compact planetary system helps distinguish Kepler-186f’s outer orbit.
Planetary mass: Planetary mass is the quantity of matter in a planet, often inferred from its gravitational effects on other bodies. Without a precise mass, Kepler-186f’s density and likely composition remain uncertain.
Transit method: The transit method detects planets by measuring periodic dips in a star’s brightness as a planet crosses its disk. Kepler-186f was identified from repeated dimming of Kepler-186.
Orbital period: An orbital period is the time an object takes to complete one orbit around another body. Kepler-186f completes an orbit around its star in about 130 days.

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Kepler-442bCompared with: It offers a smaller-planet comparison around a cooler host star.