LHS 1678: A Nearby Red Dwarf with Three Small Worlds

LHS 1678 is an M2.0 V star, a small, cool red dwarf, located 64.8 light-years away. Its reported mass estimate is 0.345 solar masses, its radius is 0.329 solar radii, and its temperature is 3490 K. These values are smaller and cooler than the Sun's. The star is estimated to be 7 billion years old. Three planets have been reported orbiting this host.

LHS 1678 b is a Sub-Earth discovered by transit in 2021. It has an orbital period of 0.86 days and a radius of 0.685 Earth radii, smaller than Earth's. LHS 1678 c, also a Sub-Earth found by transit in 2021, orbits every 3.69 days with a radius of 0.941 Earth radii, also smaller than Earth's. LHS 1678 d, another Sub-Earth, was discovered by transit in 2024 and has an orbital period of 4.97 days and a radius of 0.981 Earth radii.

Among the listed planets, LHS 1678 b has the shortest year and the smallest radius by reported estimates. LHS 1678 c has the second-shortest year and the second-smallest radius. LHS 1678 d has the longest year and the largest radius. A transit occurs when a planet passes in front of its star from our viewpoint, causing a small dip in observed brightness.