Two Neptune-Like Worlds Around TOI-1438

TOI-1438 is a K0 V main-sequence star 360 light-years from us. A K-type dwarf is a cool, orange star, cooler than the Sun. The star holds an age of 2.2 billion years, a mass of 0.886 solar masses, a radius of 0.817 solar radii, and a temperature of 5240 K. Its mass, radius, and temperature are all smaller or cooler than the Sun's. Two planets are known to orbit this host star.

TOI-1438 b and TOI-1438 c are both Neptune-like planets, a size class that reaches 4 times Earth's radius. Both were found by transit, the dimming of a star's light when a planet crosses in front of it, and both were reported in 2025.

TOI-1438 b has a mass of 9.4 Earth masses, a radius of 3.04 Earth radii, and an orbital period of 5.14 days. Its mean density is 1.84 g/cm³, 0.335 times Earth's. Both its mass and its radius are larger than Earth's. Among the listed planets, it has the shortest year and the largest radius, and it has the smallest reported mass.

TOI-1438 c has a mass of 10.6 Earth masses, a radius of 2.75 Earth radii, and an orbital period of 9.43 days. Its mean density is 2.81 g/cm³, 0.51 times Earth's. Its mass and radius are also larger than Earth's. Among the listed planets, it has the longest year, the smallest radius, and the largest reported mass.