Kepler-1669 and Its Three Planets

Kepler-1669 is a star 1770 light-years away with three known planets. The star has a reported mass of 0.57 solar masses, a radius of 0.56 solar radii, and a temperature of 4060 K. Its mass and radius are smaller than the Sun's, and its temperature is cooler than the Sun's. All three planets were found by the transit method, in which a planet passes in front of its star from our viewpoint and causes a small dip in observed brightness; repeated dips help establish orbital periods.

Kepler-1669 b is a Neptune-like planet discovered in 2020. Its orbital period is 9.51 days, and its radius is 2.78 Earth radii, larger than Earth's. Among the listed planets, it has the longest year and the largest radius.

Kepler-1669 c is a Super-Earth discovered in 2021. Its orbital period is 1.61 days, and its radius is 1.9 Earth radii, larger than Earth's. Among the listed planets, it has the shortest year and the second-smallest radius.

Kepler-1669 d is an Earth-like planet discovered in 2023. Its orbital period is 4.73 days, and its radius is 1.22 Earth radii, larger than Earth's. Among the listed planets, it has the second-shortest year and the smallest radius.

Planet size classes compare radius with Earth's: an Earth-like planet stays within 1.5 times Earth's radius, a Super-Earth reaches 2.5 times, and a Neptune-like planet reaches 4 times. The three planets share the same discovery method, and Kepler-1669 d has the second-shortest year among them by reported estimates.