About this world
HD 20781 b is an Earth-sized planet orbiting HD 20781, an orange dwarf (type K0V) 117 light-years from Earth. It is about 1.2 times the size of Earth (its size estimated from its mass), with at least 1.9 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 5.31 days at 0.053 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 1,006 K (733 °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 2019 by radial velocity with La Silla Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. HD 20781 has 4 known planets; the others are HD 20781 c, HD 20781 d and HD 20781 e.