HATS-15: A Sun-Like Star and Its Giant Planet

HATS-15 is a G9 V star, a main-sequence dwarf somewhat cooler and smaller than the Sun, located 3720 light-years away. It is 11 billion years old, with a mass of 0.871 solar masses, a radius of 0.922 solar radii, and a temperature of 5310 K, the reported mass and radius estimates being smaller than the Sun's and the temperature cooler.

The system's one known planet is HATS-15 b, discovered in 2016 by the transit method, in which a planet passes in front of its star from our viewpoint and produces a small dip in observed brightness. Classified as Jupiter-like, meaning its radius exceeds four times Earth's, HATS-15 b has a radius of 12.4 Earth radii and a mass of 690 Earth masses, roughly 2.17 times Jupiter's mass, both larger than Earth's corresponding values. It completes an orbit in 1.75 days, and its mean density is 2 g/cm³, 0.363 times Earth's.