About this world
Kepler-42 d is an Earth-sized planet orbiting Kepler-42, a cool red dwarf (type M) 131 light-years from Earth. It is about 0.57 times the size of Earth and holds 0.36 Earth masses. It completes an orbit every 1.87 days at 0.015 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 450 K (177 °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.
It was discovered in 2011 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-42 has 3 known planets; the others are Kepler-42 c and Kepler-42 b.