K2-208: A Cool, Older Star With One Known Super-Earth

K2-208 is a star 838 light-years away with one known planet. It is 6.1 billion years old, has 0.881 solar masses and 0.872 solar radii, and a temperature of 5500 K, making it less massive, smaller, and cooler than the Sun.

The planet, K2-208 b, was discovered in 2018 by the transit method. A transit occurs when a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness. Repeated dips help establish orbital periods. K2-208 b completes an orbit every 4.19 days, and its radius of 1.67 Earth radii is larger than Earth's. That radius places it in the Super-Earth size class, which reaches 2.5 times Earth's radius. Planet size classes compare radius with Earth's; they do not indicate composition.