HD 176986 and Its Three Known Planets

HD 176986 is a K2.5 V star located 90.6 light-years from Earth. Its spectral type identifies it as a K-type main-sequence dwarf. The star is estimated to be 4.3 billion years old, with a mass of 0.789 solar masses, a radius of 0.782 solar radii, and a temperature of 4930 K. Its reported mass and radius are smaller than the Sun's, and its temperature is cooler than the Sun's. Three planets are known to orbit it.

All three planets were discovered by the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion; repeated wobbles reveal the planet and its orbital period. HD 176986 b was discovered in 2017, along with HD 176986 c; HD 176986 d was discovered in 2026. Each has a minimum mass, meaning a lower bound on its true mass, of 5.36, 9.75, and 6.76 Earth masses respectively. All three are therefore more massive than Earth at minimum.

HD 176986 b orbits in 6.49 days, the shortest orbital period among the listed planets. HD 176986 c orbits in 16.8 days, the second-shortest period among the listed planets. HD 176986 d orbits in 61.4 days, the longest among the listed planets. Among the listed planets, HD 176986 b has the smallest minimum mass, at 5.36 Earth masses, while HD 176986 c has the largest, at 9.75 Earth masses. HD 176986 d has the second-smallest minimum mass, at 6.76 Earth masses.