Kepler-87: A Distant Star With Two Giant Planets

Kepler-87 is a star located 4020 light-years away. It has an age of 7.24 billion years, a mass of 1.11 solar masses, a radius of 1.8 solar radii, and a temperature of 5650 K. Its reported mass and radius estimates are larger than the Sun's, while its reported temperature is cooler. Two planets have been found orbiting this host.

Both planets were discovered by transit, which occurs when a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness. Kepler-87 b and Kepler-87 c were both announced in 2013. Because a transit is observed from our line of sight, repeated dips help establish a planet's orbital period, the time it takes to complete one orbit.

Kepler-87 b is classified as Jupiter-like, a size class for planets whose radius exceeds 4 Earth radii. Its radius is 13.5 Earth radii, larger than Earth's. Its mass is 324 Earth masses, also larger than Earth's, and its mean density is 0.728 g/cm³, 0.132 times Earth's. It completes an orbit in 115 days. Among the listed planets, Kepler-87 b has the shortest year by reported estimates, the largest radius by reported estimates, and the largest reported mass.

Kepler-87 c is also classified as Jupiter-like. Its radius is 6.14 Earth radii, larger than Earth's, and its mass is 6.4 Earth masses, larger than Earth's. Its mean density is 0.152 g/cm³, 0.0276 times Earth's. Kepler-87 c orbits in 191 days. Among the listed planets, it has the longest year by reported estimates, the smallest radius by reported estimates, and the smallest reported mass.