About this world
Proxima Cen d is an Earth-sized planet orbiting Proxima Cen, a cool red dwarf (type M5.5V) 4.24 light-years from Earth. It is about 0.69 times the size of Earth (its size estimated from its mass), with at least 0.26 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 5.12 days at 0.029 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 282 K (9 °C): too cold 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 2025 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. Proxima Cen has 2 known planets; the others are Proxima Cen b.