TOI-1203 and Its Four Known Worlds

TOI-1203 is a G3 V star located 212 light-years away, a Sun-like main-sequence dwarf with a spectral class indicating it is somewhat cooler and less massive than the Sun. Its mass is 0.886 solar masses, which is smaller than the Sun's, while its radius of 1.18 solar radii is larger than the Sun's. The star's temperature is 5740 K, and its age is 12.5 billion years. Four planets are known to orbit this host.

TOI-1203 b is a Super-Earth discovered in 2025 via the radial velocity method, which measures the gravitational wobble a planet induces in its star. Its orbital period is 4.16 days, the shortest among the listed planets. Its radius is 1.52 Earth radii, larger than Earth's, and its mass is 3.51 Earth masses, also larger than Earth's. Its mean density is 5.51 g/cm³, 0.999 times Earth's.

TOI-1203 c was also discovered in 2025 via radial velocity, with an orbital period of 13.1 days - the second-shortest among the listed planets. Its minimum mass is 5.46 Earth masses, a lower bound on its true mass, and is larger than Earth's.

TOI-1203 e, likewise found in 2025 via radial velocity, has an orbital period of 205 days, the longest among the listed planets. Its minimum mass is 42.1 Earth masses, larger than Earth's.

TOI-1203.01 is a Neptune-like planet discovered in 2021 via the transit method, which detects the small dip in starlight as a planet crosses in front of its star. Its orbital period is 25.5 days, the second-longest among the listed planets. Its radius is 2.92 Earth radii, larger than Earth's, and its mass is 7.39 Earth masses, also larger than Earth's. Its mean density is 1.64 g/cm³, 0.297 times Earth's.