TOI-500 and Its Four Known Planets

TOI-500 is a K6 V star, a main-sequence dwarf somewhat cooler and smaller than the Sun, located 155 light-years away. Its spectral type places it in the K class, cooler than G-type stars like the Sun. The star has a measured mass of 0.74 solar masses and a radius of 0.678 solar radii, both smaller than the Sun's corresponding values. Its temperature is 4440 K, cooler than the Sun's, and its age is 5 billion years.

Four planets are known to orbit TOI-500. TOI-500 b was found by the transit method in 2022. It is classified as Earth-like, with a radius of 1.17 Earth radii and a mass of 1.42 Earth masses, both larger than Earth's. Its mean density is 4.94 g/cm³, 0.896 times Earth's. It completes one orbit in just 0.548 days, the shortest period among the four planets.

The remaining three planets were each discovered by the radial velocity method in 2022, which detects the gravitational wobble a planet induces in its star. TOI-500 c has a minimum mass of 5.03 Earth masses and an orbital period of 6.64 days. TOI-500 d has a minimum mass of 33.1 Earth masses and a period of 26.2 days. TOI-500 e has a minimum mass of 15.1 Earth masses and a period of 61.3 days, the longest among the group. Each minimum mass is larger than Earth's; these are lower bounds rather than exact values, since radial velocity measurements alone cannot pin down a planet's true mass.