Kepler-172: A Distant Star With Four Known Worlds

Kepler-172 is a star located 2700 light-years away. It has 1.03 solar radii and 1 solar masses, and its reported temperature is 5600 K, which is cooler than the Sun's. The star is 6.46 billion years old. Four planets are known to orbit this host: Kepler-172 b, Kepler-172 c, Kepler-172 d, and Kepler-172 e. All four were discovered by transit, the method in which a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness, and all four were reported in 2014.

Kepler-172 b is a Super-Earth with a radius of 2.35 Earth radii and an orbital period of 2.94 days. Kepler-172 c is a Neptune-like planet with a radius of 2.86 Earth radii and an orbital period of 6.39 days. Kepler-172 d is a Super-Earth with a radius of 2.25 Earth radii and an orbital period of 14.6 days. Kepler-172 e is a Neptune-like planet with a radius of 2.76 Earth radii and an orbital period of 35.1 days. All four planets have reported radius estimates larger than Earth's.

Among the listed planets, Kepler-172 b has the shortest year by reported estimates, at 2.94 days, and Kepler-172 e has the longest, at 35.1 days. Kepler-172 c has the second-shortest year, at 6.39 days, while Kepler-172 d has the second-longest, at 14.6 days. In radius, Kepler-172 d has the smallest by reported estimates, at 2.25 Earth radii, and Kepler-172 c has the largest, at 2.86 Earth radii. Kepler-172 b has the second-smallest radius, at 2.35 Earth radii, and Kepler-172 e has the second-largest, at 2.76 Earth radii.