HD 15906 and Its Two Planets

HD 15906 is a K V star 149 light-years away. Its spectral type places it among the cooler, redder K-class stars, and the trailing V marks it as a main-sequence dwarf. Astronomers report its mass at 0.79 solar masses, its radius at 0.762 solar radii, and its temperature at 4760 K, making it less massive, smaller, and cooler than the Sun. Two planets are known to orbit this host.

Both planets were discovered by transit in 2023, the method in which a planet crosses in front of its star from our viewpoint and causes a small dip in observed brightness. HD 15906 b is a Super-Earth with a radius of 2.24 Earth radii and an orbital period of 10.9 days. HD 15906 c is Neptune-like, with a radius of 2.93 Earth radii and an orbital period of 21.6 days. The two are respectively the smallest and largest among the listed planets by radius, and their years are the shortest and longest among the listed planets by reported estimates. Both radii exceed Earth's.