K2-90 b and c: Two Transiting Worlds Around a Cool Dwarf

K2-90 is a star located 438 light-years away, and it hosts two known planets. The star itself is a relatively small and cool object, with a reported mass estimate of 0.647 solar masses, a radius estimate of 0.651 solar radii, and a temperature of 4130 K. Each of these values is smaller or cooler than the corresponding value for the Sun.

Both planets were discovered by the transit method, in which a planet passes in front of its star and causes a small dip in observed brightness. Repeated dips help establish orbital periods. K2-90 b is classified as Neptune-like, with a radius estimate of 2.6 Earth radii and an orbital period of 13.7 days. K2-90 c is classified as Earth-like, with a radius estimate of 1.3 Earth radii and an orbital period of 2.9 days. Both planets have radii larger than Earth's.

Among the listed planets, K2-90 c has the shortest year, at 2.9 days, and the smallest radius, at 1.3 Earth radii. K2-90 b has the longest year, at 13.7 days, and the largest radius, at 2.6 Earth radii.