TOI-199 and Its Two Worlds

TOI-199 is a star 334 light-years away with a spectral type of G9 V, a Sun-like class that marks it as a main-sequence dwarf. Its age is 0.8 billion years old. It is less massive than the Sun at 0.936 solar masses and smaller than the Sun at 0.82 solar radii, and its temperature of 5260 K is cooler than the Sun's. Two planets orbit this host.

TOI-199 b was discovered in 2023 by the transit method, in which a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness. This planet is Jupiter-like, a size class for worlds exceeding 4 times Earth's radius, and its radius estimate of 9.08 Earth radii is larger than Earth's. Its mass estimate of 54 Earth masses is also larger than Earth's, and its mean density is 0.398 g/cm³, 0.0722 times Earth's. It completes an orbit every 105 days, the shortest period among the listed planets.

TOI-199 c was also discovered in 2023, but by transit timing variations. Its mass estimate of 89 Earth masses is larger than Earth's, making it the most massive of the listed planets. It takes 274 days to orbit its star, the longest year among the listed planets.