HD 81817 and Its Two Known Planets

HD 81817 is a K3 III star 878 light-years away. It is 0.15 billion years old, with a mass of 4.3 solar masses and a radius of 83.8 solar radii, and its temperature is 4140 K. Its reported mass and radius estimates are larger than the Sun's, and its reported temperature is cooler. Two planets are known to orbit it.

Both planets were found by radial velocity, which detects the wobble a planet's gravity induces in its star's motion. HD 81817 b was discovered in 2020, and HD 81817 c in 2022. HD 81817 b has a mass of 7670 Earth masses and an orbital period of 1020 days, roughly 24.1 times Jupiter's mass and larger than Earth's. HD 81817 c has a minimum mass, a lower bound on its true mass, of 7190 Earth masses, and an orbital period of 623 days; its minimum mass is roughly 22.6 times Jupiter's mass and larger than Earth's. Among the listed planets, HD 81817 c has the shortest year by reported estimates, and HD 81817 b has the longest.