TOI-1117: A Sun-Like Star With Three Known Planets

TOI-1117 is a G-type main-sequence dwarf, a Sun-like star, located 547 light-years away. It is 4.42 billion years old, with a reported mass estimate of 0.97 solar masses, a radius of 1.05 solar radii, and a temperature of 5640 K. Its reported mass is smaller than the Sun's, its radius is larger, and its temperature is cooler. Three planets are known to orbit this host.

TOI-1117 b is a Super-Earth discovered by the transit method in 2025. It has a mass of 8.9 Earth masses and a radius of 2.46 Earth radii, both larger than Earth's, with a mean density of 3.29 g/cm³, 0.598 times Earth's. Its orbital period is 2.23 days, the shortest among the listed planets. This period and the repeated brightness dips that established it are typical of transit detections, which occur when a planet crosses in front of its star from our viewpoint.

TOI-1117 c was discovered by the radial velocity method in 2025 and has a minimum mass of 8.78 Earth masses, larger than Earth's, with an orbital period of 4.58 days, the second-shortest among the listed planets. TOI-1117 d was also found by radial velocity in 2025, with a minimum mass of 10.7 Earth masses, larger than Earth's, and an orbital period of 8.66 days, the longest among the listed planets.

The radial velocity method detects the wobble a planet's gravity induces in its star's motion; repeated wobbles reveal the planet and its orbital period. Both minimum masses are lower bounds on the planets' true masses. The three reported orbital periods are among the shortest known.