Kepler-277 and Its Two Neptune-Like Planets

Kepler-277 is a star located 3190 light-years away. It is 4.07 billion years old and has a mass of 1.21 solar masses and a radius of 1.57 solar radii, both larger than the Sun's corresponding values. Its temperature of 6060 K is hotter than the Sun's. Two planets are known to orbit this star, both 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 planets are classified as Neptune-like, a size class reaching 4 times Earth's radius. Kepler-277 b has a radius of 2.92 Earth radii and a mass of 87.3 Earth masses, both larger than Earth's, and orbits every 17.3 days. Kepler-277 c has a radius of 3.36 Earth radii and a mass of 64.2 Earth masses, both larger than Earth's, with an orbital period of 33 days. Among the listed planets, Kepler-277 b has the shortest year and the smallest radius, while Kepler-277 c has the longest year, the largest radius, and the smallest reported mass. Kepler-277 b has the largest reported mass. Kepler-277 b's mean density is 19.3 g/cm³, 3.51 times Earth's, while Kepler-277 c's is 9.33 g/cm³, 1.69 times Earth's.