The GJ 163 System: A Cool Dwarf and Its Three Worlds

GJ 163 is a star located 49.3 light-years from Earth. Its spectral type, M3.5 V, marks it as a small, cool red dwarf, and its reported temperature of 3500 K is cooler than the Sun's. The star's reported mass estimate is 0.4 solar masses, smaller than the Sun's, and its age is 6 billion years. Three planets are known to orbit this host, all discovered in 2013 by the radial velocity method, which detects the wobble a planet's gravity induces in its star's motion.

GJ 163 b has a minimum mass of 10.6 Earth masses and an orbital period of 8.63 days. That period is the shortest among the listed planets. Its minimum mass is larger than Earth's and is the second-smallest among the three worlds.

GJ 163 c has an orbital period of 25.6 days, the second-shortest among the listed planets. Its minimum mass is 6.8 Earth masses, larger than Earth's and the smallest of the trio.

GJ 163 d has the longest orbital period among the listed planets at 604 days. Its minimum mass of 29.4 Earth masses is the largest of the three and, like the others, exceeds Earth's minimum mass.

A minimum mass is a lower bound on a planet's true mass, so the actual masses of all three worlds remain at least these values.