HD 217107 and Its Two Known Planets

HD 217107 is a star located 65.4 light-years from us. It is a single star with a spectral type of G8IV/V, and its reported properties include an age of 5.84 billion years, a mass of 1.11 solar masses, a radius of 1.08 solar radii, and a temperature of 5700 K. The host star is cooler than the Sun, while its reported mass and radius estimates are both larger than the Sun's. Two planets have been found orbiting HD 217107.

HD 217107 b was discovered in 1998 using the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion. It has a mass of 460 Earth masses and an orbital period of 7.13 days. Among the listed planets, HD 217107 b has the shortest year and the smallest reported mass. Its mass is roughly 1.45 times Jupiter's mass.

HD 217107 c was discovered in 2005, also through radial velocity measurements. It has a mass of 1390 Earth masses and an orbital period of 5140 days. Among the listed planets, HD 217107 c has the longest year and the largest reported mass, and its mass is roughly 4.37 times Jupiter's mass. Both planets' reported mass estimates are larger than Earth's.