HD 3167: A Quiet K-Type Star and Its Four Worlds

HD 3167 is a K0 V star located 154 light-years away. This spectral type marks a main-sequence dwarf somewhat cooler and redder than the Sun. The star's reported mass estimate is 0.852 solar masses and its radius estimate is 0.871 solar radii, both smaller than the Sun's, while its temperature of 5300 K is cooler than the Sun's. It is also ancient, with an age of 10.2 billion years. Four planets orbit this host.

HD 3167 b is a Super-Earth discovered by transit in 2016. Its radius of 1.6 Earth radii is larger than Earth's, its mass estimate of 4.84 Earth masses is larger than Earth's, and its mean density is 6.5 g/cm³, 1.18 times Earth's. It completes an orbit in 0.96 days, the shortest year among the listed planets. HD 3167 c, also found by transit in 2016, is Neptune-like, with a radius of 2.98 Earth radii and a mass estimate of 11.4 Earth masses, both larger than Earth's. Its mean density is 2.37 g/cm³, 0.43 times Earth's, and its orbital period of 29.8 days is the second-longest year among the listed planets.

Two further planets were detected by the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion. HD 3167 d, discovered in 2017, has a mass estimate of 7.3 Earth masses, larger than Earth's, and orbits in 8.4 days, the second-shortest year among the listed planets. HD 3167 e, discovered in 2022, has a mass estimate of 14.9 Earth masses, the largest among the listed planets, and a period of 91.9 days, the longest year among the listed planets.