About this world
GJ 3998 b is a super-Earth orbiting GJ 3998, a cool red dwarf (type M1) 59.2 light-years from Earth. It is about 1.4 times the size of Earth (its size estimated from its mass), with at least 2.5 Earth masses (a minimum, measured by radial velocity). It completes an orbit every 2.65 days at 0.03 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 734 K (460 °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 2016 by radial velocity with Roque de los Muchachos Observatory. The star wobbles toward and away from us, Doppler-shifting its spectrum. GJ 3998 has 3 known planets; the others are GJ 3998 c and GJ 3998 d.