Kepler-20: A Six-Planet System in the Kepler Field

Kepler-20 is a star 922 light-years away with six known planets. The star has a reported age of 8.8 billion years, a mass of 0.912 solar masses, a radius of 0.944 solar radii, and a temperature of 5470 K. Its mass and temperature are both lower than the Sun's. All six planets orbit this host.

Kepler-20 b is a Super-Earth discovered by transit in 2011. It has a mass of 9.7 Earth masses, an orbital period of 3.7 days, and a radius of 1.77 Earth radii. Its radius and mass are larger than Earth's, and its mean density is 9.59 g/cm³, 1.74 times Earth's. Among the listed planets, Kepler-20 b has the shortest year.

Kepler-20 c and Kepler-20 d are Neptune-like planets, both discovered by transit in 2011. Kepler-20 c has a mass of 11.1 Earth masses, an orbital period of 10.9 days, and a radius of 2.89 Earth radii. Its radius and mass are larger than Earth's, and its mean density is 2.52 g/cm³, 0.458 times Earth's. Kepler-20 d has a mass of 13.4 Earth masses, an orbital period of 77.6 days, and a radius of 2.61 Earth radii. Its size and mass are also larger than Earth's, and its mean density is 4.17 g/cm³, 0.757 times Earth's. Among the listed planets, Kepler-20 d has the longest year.

Kepler-20 e and Kepler-20 f are Sub-Earth planets, both discovered by transit in 2011. Kepler-20 e has a reported upper limit of 0.76 Earth masses, an orbital period of 6.1 days, and a radius of 0.821 Earth radii. Its radius is smaller than Earth's, and among the listed planets it has the second-shortest year. Kepler-20 f has a reported upper limit of 1.4 Earth masses, an orbital period of 19.6 days, and a radius of 0.952 Earth radii, also smaller than Earth's.

Kepler-20 g was discovered by radial velocity in 2016. It has a minimum mass of 20 Earth masses and an orbital period of 34.9 days, the second-longest among the listed planets. Its minimum mass is larger than Earth's.