YZ Cet: A Nearby Red Dwarf with Three Small Worlds

YZ Cet is a star located 12.1 light-years from Earth. It has a spectral type of M4.5 V, making it a small, cool red dwarf. The star's reported mass estimate is smaller than the Sun's, at 0.142 solar masses, and its reported radius estimate is smaller than the Sun's, at 0.157 solar radii. Its temperature is 3150 K, which is cooler than the Sun's, and its age is 3.8 billion years. Three planets are known to orbit this host: YZ Cet b, YZ Cet c, and YZ Cet d.

All three planets were discovered in 2017 using the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion. YZ Cet b has a minimum mass of 0.7 Earth masses, a lower bound on its true mass, and an orbital period of 2.02 days. Its minimum mass is smaller than Earth's. YZ Cet c has a minimum mass of 1.14 Earth masses and an orbital period of 3.06 days, and its minimum mass is larger than Earth's. YZ Cet d has a minimum mass of 1.09 Earth masses and an orbital period of 4.66 days.

Among the listed planets, YZ Cet b has the shortest year by reported estimates, at 2.02 days, and the smallest minimum mass, at 0.7 Earth masses. YZ Cet c has the second-shortest year, at 3.06 days, and the largest minimum mass, at 1.14 Earth masses. YZ Cet d has the longest year, at 4.66 days, and the second-smallest minimum mass, at 1.09 Earth masses.