Kepler-307: A Cool Star With Two Super-Earths

Kepler-307 is a star located 1880 light-years away, and two planets have been found orbiting it. The host star is estimated to be 6.61 billion years old, with a mass of 0.94 solar masses and a radius of 0.95 solar radii. Its reported temperature is 5510 K, which is cooler than the Sun's, and its reported mass estimate is smaller than the Sun's.

Both planets were discovered by transit in 2013. 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. Both Kepler-307 b and Kepler-307 c are classified as Super-Earths, a size class that reaches up to 2.5 times Earth's radius.

Kepler-307 b has a mass of 7.44 Earth masses and a radius of 2.43 Earth radii, both larger than Earth's corresponding values. Its orbital period is 10.4 days, and its mean density is 2.86 g/cm³, 0.519 times Earth's. Among the listed planets, it has the shortest year and the largest radius and reported mass.

Kepler-307 c has a mass of 3.64 Earth masses and a radius of 2.2 Earth radii, also larger than Earth's. Its orbital period is 13.1 days, and its mean density is 1.88 g/cm³, 0.342 times Earth's. Among the listed planets, it has the longest year and the smallest radius and reported mass.