Kepler-222: A Distant Star With Three Worlds

Kepler-222 is a star located 2480 light-years away. It has a reported age of 4.79 billion years, a mass of 0.88 solar masses, a radius of 0.84 solar radii, and a temperature of 5300 K. Its mass and radius are smaller than the Sun's, and its temperature is cooler. Three planets are known to orbit this host: Kepler-222 b, Kepler-222 c, and Kepler-222 d.

Kepler-222 b is a Neptune-like planet discovered by transit in 2014. It has an orbital period of 3.94 days and a radius of 3.16 Earth radii. Among the listed planets, it has the shortest orbital period and the smallest radius.

Kepler-222 c is a Jupiter-like planet, also discovered by transit in 2014. It orbits every 10.1 days and has a radius of 4.64 Earth radii. Among the listed planets, it has the second-shortest orbital period and the largest radius. Its radius exceeds 4 times Earth's radius, placing it in the Jupiter-like class.

Kepler-222 d is a Neptune-like planet discovered by transit in 2014. Its orbital period is 28.1 days, and its radius is 3.69 Earth radii. Among the listed planets, it has the longest orbital period and the second-smallest radius.

The reported radii of all three planets are larger than Earth's. The star's reported mass estimate is smaller than the Sun's, as is its radius estimate, and its reported temperature is cooler than the Sun's.

Earth radii compare radius, not volume. A transit occurs when a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness; repeated dips help establish orbital periods. An orbital period is the time a planet takes to complete one orbit: its year. A light-year is a unit of distance. Solar masses and radii compare stellar mass and radius with the Sun.