KOI-1599: A Two-Planet System in the Distant Sky

KOI-1599 is a star located 3690 light-years from Earth. It has 1.02 solar masses, 0.972 solar radii, and a temperature of 5820 K. Two planets are known to orbit this host, both discovered in 2019 by the transit method, in which a planet passing in front of its star from our viewpoint causes a small dip in observed brightness.

The two planets are KOI-1599.01 and KOI-1599.02, and both are classified as Super-Earths, a size class that reaches up to 2.5 times Earth's radius. KOI-1599.01 has a mass of 4.6 Earth masses and a radius of 1.9 Earth radii, and its reported mass and radius estimates are larger than Earth's. It completes an orbit in 20.4 days, the longest year among the listed planets. Its mean density is 3.7 g/cm³, 0.671 times Earth's.

KOI-1599.02 has a mass of 9 Earth masses and a radius of 1.9 Earth radii, with reported mass and radius estimates also larger than Earth's. Its orbital period is 13.6 days, the shortest year among the listed planets. Its mean density is 7.23 g/cm³, 1.31 times Earth's.

Among the listed planets, KOI-1599.01 has the smallest reported mass at 4.6 Earth masses, and KOI-1599.02 has the largest reported mass at 9 Earth masses.