The Kepler-276 System: Three Neptune-Like Worlds

Kepler-276 is a star located 3730 light-years away, and it hosts three known planets. The star itself is 3.8 billion years old and has a mass of 1.02 solar masses and a radius of 1.03 solar radii, with a temperature of 5830 K.

All three planets are Neptune-like in size classification and were found by the transit method. Kepler-276 b was discovered in 2014 and has a radius of 2.87 Earth radii and an orbital period of 14.1 days. Kepler-276 c was discovered in 2013 and has a mass of 16.6 Earth masses, a radius of 2.9 Earth radii, and an orbital period of 31.9 days. Kepler-276 d was also discovered in 2013 and has a mass of 16.3 Earth masses, a radius of 2.8 Earth radii, and an orbital period of 48.6 days.

Among the listed planets, Kepler-276 b has the shortest year, at 14.1 days, followed by Kepler-276 c with the second-shortest year, at 31.9 days. Kepler-276 d has the longest year, at 48.6 days. In radius, Kepler-276 c is the largest, at 2.9 Earth radii, while Kepler-276 d is the smallest, at 2.8 Earth radii, and Kepler-276 b is second-smallest, at 2.87 Earth radii. The masses of Kepler-276 c and Kepler-276 d are both larger than Earth's, and the radii of all three planets are larger than Earth's. Kepler-276 c has a mean density of 3.75 g/cm³, 0.681 times Earth's, while Kepler-276 d has a mean density of 4.09 g/cm³, 0.743 times Earth's.