Kepler-289 and Its Four Planets

Kepler-289 is a star located 2300 light-years away. It is 0.65 billion years old and has 1.08 solar masses, 1 solar radii, and a temperature of 5990 K. Its reported mass estimate is larger than the Sun's, and its reported temperature is hotter than the Sun's. Four planets are known to orbit this star.

Kepler-289 b, Kepler-289 c, Kepler-289 d, and Kepler-289 e were all found by transit, which occurs when a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness, with repeated dips helping to establish orbital periods. Kepler-289 b, Kepler-289 c, and Kepler-289 d were discovered in 2014, while Kepler-289 e was discovered in 2025. Among the listed planets, Kepler-289 b has the shortest year by reported estimates at 34.5 days, followed by Kepler-289 d with the second-shortest year at 66 days. Kepler-289 c has the second-longest year at 126 days, and Kepler-289 e has the longest year at 330 days. Among the listed planets, Kepler-289 b has the smallest reported mass at 3.7 Earth masses, Kepler-289 d has the second-smallest reported mass at 5.33 Earth masses, Kepler-289 e has the second-largest reported mass at 17.4 Earth masses, and Kepler-289 c has the largest reported mass at 157 Earth masses.

Kepler-289 b is a Super-Earth with a radius of 2.49 Earth radii and a mass of 3.7 Earth masses. Its reported radius estimate and reported mass estimate are both larger than Earth's, and its mean density is 1.32 g/cm³, 0.24 times Earth's. Kepler-289 c is Jupiter-like, with a radius of 11.2 Earth radii and a mass of 157 Earth masses. Its reported radius estimate and reported mass estimate are both larger than Earth's, and its mean density is 0.612 g/cm³, 0.111 times Earth's. Kepler-289 d is Neptune-like, with a radius of 3.03 Earth radii and a mass of 5.33 Earth masses. Its reported radius estimate and reported mass estimate are both larger than Earth's, and its mean density is 1.06 g/cm³, 0.192 times Earth's. Kepler-289 e has a mass of 17.4 Earth masses, which is larger than Earth's, and an orbital period of 330 days.