Kepler-638 is a star with 0.88 times the mass of the Sun, and 0.93 times its radius. It is located 3232.90 light years away from the solar system and is estimated to be 11.75 billion years old, as compared to the Sun which is roughly 4.6 billion years old.
Kepler-638 is known to have 1 exoplanets in orbit around it.
Kepler-638 b was discovered by the Kepler observatory, in 2016-05, using the transit method. Its semi-major axis is 0.06 astronomical units, as compared to Earth's which is 1 astronomical unit. The mass of Kepler-638 b is 4.007 times the mass of Earth. The radius of Kepler-638 b is 1.830 that of Earth. At 4.007 Earth masses, Kepler-638 b is a so called Super Earth. Super Earths could be terrestrial worlds like Earth, but they could also be ocean worlds or terrestrial worlds wrapped in a substantial atmosphere, in which case some refer to them as Mini Neptunes. No Super Earths are known to exist in our solar system, but if it exists, the so-called Planet Nine could very well be a super Earth, as it is hypothesized to have a mass between five and ten Earth masses.