K2-257 is a star with 0.52 times the mass of the Sun, and 0.5 times its radius. It is located 208.76 light years away from the solar system.
K2-257 is known to have 1 exoplanets in orbit around it.
K2-257 b was discovered by the K2 observatory, in 2018-08, using the transit method. Its semi-major axis is 0.02 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of K2-257 b is 0.499 times the mass of Earth. The radius of K2-257 b is 0.830 that of Earth. At less than 1.5 Earth masses, K2-257 b is a regular terrestrial planet, much like the terrestrial planets we find in our solar system, namely Mercury, Venus, Earth and Mars.