Imaginary Picture of GJ 251 b

Display orbital revolution of GJ 251 b around the hoststar GJ 251
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Exoplanet Name : GJ 251 b
Alternate Name : HD 265866 b
Status : Confirmed
Radius (Rjup / Re): 0.1299 (Rjup) 1.4558 (Rearth)
Mass (Mjup / Me): 0.0130 (Mjup) 4.1332 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0818 (AU) 0.0818 (AU Est.)
Eccentricity : 0.1000
Orbital Period(Yrs) 0.0390
Orbital Period(Observed/Estimated) 14.24 (Days Obs.) 14.24 (Days Est.)
Surface Gravity (G Earth) 1.9503
Star Radiation at Atmospheric Boundary: 3444.1 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 341.9 (K)
Blackbody T 0.3(K) 321.1 (K)
Blackbody T 0.7(K) 259.8 (K)
Tidally Locked Blackbody T 0.1(K) 406.6 (K)
Tidally Locked Blackbody T 0.3(K) 381.8 (K)
Size Class: super-Earth-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 251
Alternate Name :
Star Distance(LY) : 18.2
Stellar Radius(Rsun) : 0.4 (Rsun Measured)
Stellar Mass(Msun) : 0.4 (Msun Measured) 0.4 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 3451 (K)
Spectral type : M3.0V
UV portion[%]: 0.3
Visible portion[%]: 13.2
IR portion[%]: 86.5
Metalicity : -0.0
Absolute Magnitude: 11.3
Apparent Magnitude: 10.0
Right Ascension(RA) 103.7040
Declination (DEC) 33.2664
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors
Discovery Paper - Title
Discovery Paper - Journal
Discovery Paper - URL
SIMBAD LINK http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=GJ+251+&submit=SIMBAD+search
Open Exoplanet Database Link
GJ 251 b
GJ 251 b

  • GJ 251 b is an exoplanet orbiting the star GJ 251, located about 18.2 light-years ( 5.6 pc) away from Solar System. Its discovery was publicly announced on 2017.
  • The host star GJ 251 has apparent magnitude of 10.0, with absolute magnitude of 11.3.
  • It is 0.4 times more massive and 0.4 times bigger compared with our Sun. The surface temperature is 3451 with its spectral types of M3.0V
  • In this planetary system, the extrasolar planet GJ 251 b orbits around the star GJ 251 every 14.2 days with its orbital distance of 0.08 AU ( 12237105.8 km)
  • (Projected orbit of GJ 251 b around its host star GJ 251)


  • The Star GJ 251 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.094 AU ( 14049129.5 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.130 AU ( 19419568.4 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.198 AU ( 29591124.7 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 0.291 AU ( 43544636.3 km)
  • Radiation at Planetary Boundary of GJ 251 b : 3444.14 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star GJ 251)



  • Kopparapu Recent Venus for Star GJ 251 distance : 0.106 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star GJ 251 distance : 0.134 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star GJ 251 distance : 0.130 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star GJ 251 distance : 0.143 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star GJ 251 distance : 0.262 AU
  • Kopparapu Outer Boundary for Early Mars for Star GJ 251 distance : 0.276 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star GJ 251)



  • Original Kopparapu Recent Venus for Star GJ 251 distance : 0.105 AU
  • Original Kopparapu Runaway Greenhouse for Star GJ 251 distance : 0.139 AU
  • Original Kopparapu Moist Greenhouse for Star GJ 251 distance : 0.139 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star GJ 251 distance : 0.266 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star GJ 251 distance : 0.277 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star GJ 251)



    (Position in Stellar Map of star GJ 251 and its Exoplanet GJ 251 b)



    (Zoomed position in Stellar Map of star GJ 251 and its Exoplanet GJ 251 b (zoom level 3))

    (Synthetic Spectrum of star GJ 251*)
    *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