About this world
Barnard b is an Earth-sized planet orbiting Barnard's star, a cool red dwarf (type M3.5-4V) 5.96 light-years from Earth. It is about 0.72 times the size of Earth (its size estimated from its mass), with at least 0.3 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 3.15 days at 0.023 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 438 K (165 °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 2024 by radial velocity with Paranal Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. Barnard's star has 4 known planets; the others are Barnard d, Barnard c and Barnard e.