HD 215152 and Its Four Known Planets

HD 215152 is a K3 V star located 70.4 light-years away. Its spectral type identifies it as a K-type main-sequence dwarf, a class of star cooler and redder than the Sun. The star has a reported mass of 0.77 solar masses and a radius of 0.73 solar radii, both smaller than the Sun's, and a temperature of 4940 K, which is cooler than the Sun's. Four planets are known to orbit this host.

All four planets were discovered in 2018 using the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion; repeated wobbles reveal the planet and its orbital period. HD 215152 b has a minimum mass of 1.82 Earth masses and an orbital period of 5.76 days, the shortest year among the listed planets. HD 215152 c has a minimum mass of 1.72 Earth masses, the smallest among the listed planets, and an orbital period of 7.28 days, the second-shortest year. HD 215152 d has a minimum mass of 2.8 Earth masses and an orbital period of 10.9 days, the second-longest year. HD 215152 e has a minimum mass of 2.88 Earth masses, the largest among the listed planets, and an orbital period of 25.2 days, the longest year.

A minimum mass is a lower bound on a planet's true mass, so each of these figures represents the least mass the planet could have. The minimum masses of HD 215152 b, d, and e are larger than Earth's.