GJ 338 B is 20.7 light-years from the Sun. The NASA Exoplanet Archive lists 1 planet around this M0 V star; the first was found in 2020 by radial velocity (Calar Alto Observatory).
Fly there in 3DGJ 338 B b goes round its star every 24.4 days, 4 times as often as Mercury goes round the Sun.
GJ 338 B is one of 2 stars in its system: the other is drawn where the Washington Double Star Catalog measures it on the sky.
| Spectral type | M0 V |
| Surface temperature | 4,014 K |
| Mass | 0.64 solar masses |
| Radius | 0.58 solar radii |
| Luminosity | 0.0792 times the Sun |
| Apparent magnitude | 7.7 |
| Age | about 4 billion years |
| Distance from the Sun | 20.7 light-years (6.3 parsecs) |
| Position (J2000) | RA 138.5917°, Dec 52.6835° |
| Constellation | Ursa Major |
GJ 338 B B is a M0V star of magnitude 7.88, with a computed orbit. In 2026 it was 16.8″ from GJ 338 B, at position angle 101° (Washington Double Star Catalog, 09144+5241 STF1321 AB): 106 AU on the sky at this distance. The true distance can only be larger.
| Planet | Year | Orbit | Radius | Mass | Found |
|---|---|---|---|---|---|
| GJ 338 B b | 24.4 days | 0.142 AU | 3.25 R⊕ estimated | 10.6 M⊕ minimum | Radial Velocity, 2020 |
Values are the NASA Exoplanet Archive’s composite parameters. A radius marked estimated comes from a mass–radius relation; a mass marked minimum is M sin i. Planet sizes and colours in the 3D view are renderings: none of these worlds has been photographed as more than a point of light.