About this world
Kepler-37 d is a sub-Neptune orbiting Kepler-37, a yellow, Sun-like star 208 light-years from Earth. It is about 2 times the size of Earth and holds 2 Earth masses. It completes an orbit every 39.8 days at 0.21 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 499 K (226 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock. Its atmosphere has already been studied: 2 spectroscopic observations.
It was discovered in 2013 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-37 has 4 known planets; the others are Kepler-37 b, Kepler-37 c and Kepler-37 e.