HD 215497 and Its Two Known Planets

HD 215497 is a K3 V star 132 light-years away with two planets. As a K-type main-sequence dwarf, it is cooler and redder than the Sun. Its reported mass is 0.872 solar masses, smaller than the Sun's, and its temperature is 5110 K, also cooler than the Sun's. An age upper limit of 7 billion years has been reported. Both planets were found in 2009 by the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion.

HD 215497 b has a minimum mass of 6.36 Earth masses and an orbital period of 3.93 days. Its minimum mass is larger than Earth's, and among the listed planets it has the shortest year. HD 215497 c has a reported mass of 111 Earth masses and an orbital period of 566 days. Its mass is larger than Earth's, and among the listed planets it has the longest year. The difference between a minimum mass, a lower bound on a planet's true mass, and an ordinary mass estimate explains why the two planets' mass values are stated differently.