TOI-5398: A Sun-Like Star with Two Transiting Worlds

TOI-5398 is a G V star located 427 light-years away. Its reported mass is 1.15 solar masses, larger than the Sun's; its radius is 1.05 solar radii, larger than the Sun's; and its temperature is 6000 K, hotter than the Sun's. Its age is 0.65 billion years. Two planets are known to orbit this star, both discovered by the transit method, which detects the small dip in brightness when a planet crosses in front of its host.

TOI-5398 c was found in 2023. It is a Neptune-like planet with a radius of 3.52 Earth radii and a mass of 11.8 Earth masses; both measurements are larger than Earth's corresponding values. Its mean density is 1.49 g/cm³, 0.271 times Earth's. It completes one orbit in 4.77 days, the shortest orbital period among the listed planets.

TOI-5398 b was found in 2022. Classified as Jupiter-like, it has a radius of 10.3 Earth radii and a mass of 58.7 Earth masses; both measurements are larger than Earth's. Its mean density is 0.296 g/cm³, 0.0537 times Earth's. It takes 10.6 days to orbit the star, the longest orbital period among the listed planets.

Among the listed planets, TOI-5398 c has the smallest radius by reported estimates and the smallest reported mass, while TOI-5398 b has the largest radius and the largest reported mass.