Imaginary Picture of GJ 338 Bb

Display orbital revolution of GJ 338 Bb around the hoststar GJ 338 B
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Exoplanet Name : GJ 338 Bb
Alternate Name : HD 79211 b
Status : Confirmed
Radius (Rjup / Re): 0.1983 (Rjup) 2.2231 (Rearth)
Mass (Mjup / Me): 0.0327 (Mjup) 10.3966 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.1420 (AU) 0.1420 (AU Est.)
Eccentricity : 0.0970
Orbital Period(Yrs) 0.0669
Orbital Period(Observed/Estimated) 24.43 (Days Obs.) 24.43 (Days Est.)
Surface Gravity (G Earth) 2.1037
Star Radiation at Atmospheric Boundary: 5263.7 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 380.2 (K)
Blackbody T 0.3(K) 357.0 (K)
Blackbody T 0.7(K) 288.9 (K)
Tidally Locked Blackbody T 0.1(K) 452.1 (K)
Tidally Locked Blackbody T 0.3(K) 424.6 (K)
Size Class: sub-Neptune-size
Mass Class:
Detection Type : Radial Velocity
Mass Detection : Radial Velocity
Radius Detection :
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : GJ 338 B
Alternate Name : HD 79211
Star Distance(LY) : 20.7
Stellar Radius(Rsun) : 0.6 (Rsun Measured)
Stellar Mass(Msun) : 0.6 (Msun Measured) 0.6 (Msun Estimated)
Star Age : 4.0 (GY)
Temperature : 4005 (K)
Spectral type : M0.0 V
UV portion[%]: 0.7
Visible portion[%]: 24.6
IR portion[%]: 74.7
Metalicity : -0.0
Absolute Magnitude: 5.8
Apparent Magnitude: 4.8
Right Ascension(RA) 138.6028
Declination (DEC) 52.6864
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors
Discovery Paper - Title
Discovery Paper - Journal
Discovery Paper - URL
SIMBAD LINK
Open Exoplanet Database Link
GJ 338 Bb
GJ 338 Bb

  • GJ 338 Bb is an exoplanet orbiting the star GJ 338 B, located about 20.7 light-years ( 6.3 pc) away from Solar System. Its discovery was publicly announced on 2020.
  • The host star GJ 338 B has apparent magnitude of 4.8, with absolute magnitude of 5.8.
  • It is 0.6 times more massive and 0.6 times bigger compared with our Sun. The surface temperature is 4005 with its spectral types of M0.0 V
  • In this planetary system, the extrasolar planet GJ 338 Bb orbits around the star GJ 338 B every 24.4 days with its orbital distance of 0.14 AU ( 21242897.6 km)
  • (Projected orbit of GJ 338 Bb around its host star GJ 338 B)


  • The Star GJ 338 B 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.202 AU ( 30150265.9 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.279 AU ( 41675546.7 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.425 AU ( 63504310.4 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 0.625 AU ( 93449374.7 km)
  • Radiation at Planetary Boundary of GJ 338 Bb : 5263.74 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star GJ 338 B)



  • Kopparapu Recent Venus for Star GJ 338 B distance : 0.226 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star GJ 338 B distance : 0.286 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star GJ 338 B distance : 0.276 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star GJ 338 B distance : 0.303 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star GJ 338 B distance : 0.542 AU
  • Kopparapu Outer Boundary for Early Mars for Star GJ 338 B distance : 0.572 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star GJ 338 B)



  • Original Kopparapu Recent Venus for Star GJ 338 B distance : 0.223 AU
  • Original Kopparapu Runaway Greenhouse for Star GJ 338 B distance : 0.295 AU
  • Original Kopparapu Moist Greenhouse for Star GJ 338 B distance : 0.295 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star GJ 338 B distance : 0.551 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star GJ 338 B distance : 0.573 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star GJ 338 B)



    (Position in Stellar Map of star GJ 338 B and its Exoplanet GJ 338 Bb)



    (Zoomed position in Stellar Map of star GJ 338 B and its Exoplanet GJ 338 Bb (zoom level 3))

    (Synthetic Spectrum of star GJ 338 B*)
    *Yamashiki YA et al. 2019 ApJ 881 114
    MUSCLES Paper I - France et al. 2016 ApJ 820 89
    MUSCLES Paper II- Youngblood et al. 2016 ApJ 824 101
    MUSCLES Paper III- Loyd et al. 2016 ApJ 824 102