K2-99: A Distant Star With Two Known Planets

K2-99 is a G0 IV star located 1690 light-years away, and two planets have been reported in orbit around it. The host star is estimated to be 2.4 billion years old, with a mass of 1.6 solar masses and a radius of 3.1 solar radii. Its temperature is 5990 K, and its reported mass, radius, and temperature estimates are each larger or hotter than the Sun's corresponding values.

The first planet, K2-99 b, was discovered by the transit method in 2016. It is a Jupiter-like planet with a mass of 277 Earth masses and a radius of 11.9 Earth radii, both larger than Earth's. Its mean density is 0.908 g/cm³, which is 0.165 times Earth's. K2-99 b completes an orbit in 18.2 days, the shortest orbital period among the listed planets.

The second planet, K2-99 c, was discovered by the radial velocity method in 2022. It has a minimum mass of 2670 Earth masses, making it roughly 8.4 times Jupiter's mass and larger than Earth's. Its orbital period is 522 days, the longest among the listed planets. A minimum mass represents a lower bound on the planet's true mass, distinct from an ordinary mass estimate.