TOI-431 and Its Three Planets

TOI-431 is a star located 106 light-years away, with three planets in orbit around it. The star has a reported mass of 0.8 solar masses, a radius of 0.727 solar radii, and a temperature of 4890 K. Each of these measurements is smaller or cooler than the corresponding value for the Sun.

TOI-431 b was discovered by the transit method in 2021. It has a mass of 3.07 Earth masses and a radius of 1.28 Earth radii, placing it within the Earth-like size class. Its orbital period is 0.49 days, the shortest among the listed planets. It also has a mean density of 8.07 g/cm³, which is 1.46 times Earth's.

TOI-431 c was also discovered in 2021, using the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion. It has a minimum mass of 2.83 Earth masses and an orbital period of 4.85 days, the second-shortest among the listed planets. Because this is a minimum mass, it represents a lower bound on the planet's true mass.

TOI-431 d was discovered by the transit method in 2021. It has a mass of 9.9 Earth masses and a radius of 3.29 Earth radii, making it Neptune-like in size. Its orbital period is 12.5 days, the longest among the listed planets. Its mean density is 1.53 g/cm³, or 0.278 times Earth's.