Imaginary Picture of Kepler-121 b

Display orbital revolution of Kepler-121 b around the hoststar Kepler-121
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Exoplanet Name : Kepler-121 b
Alternate Name : "2MASS J19043889+3940407 b, K00223.01, KIC 4545187 b, KOI-223 b, KOI-223.01, WISE J190438.90+394040.9 b"
Status : Confirmed
Radius (Rjup / Re): 0.2090 (Rjup) 2.3427 (Rearth)
Mass (Mjup / Me): 0.0183 (Mjup) 5.8230 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0390 (AU) 0.0390 (AU Est.)
Eccentricity : 0.0000
Orbital Period(Yrs) 0.0087
Orbital Period(Observed/Estimated) 3.18 (Days Obs.) 3.54 (Days Est.)
Surface Gravity (G Earth) 1.0610
Star Radiation at Atmospheric Boundary: 300996.8 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 1045.4 (K)
Blackbody T 0.3(K) 981.7 (K)
Blackbody T 0.7(K) 794.3 (K)
Tidally Locked Blackbody T 0.1(K) 1243.2 (K)
Tidally Locked Blackbody T 0.3(K) 1167.5 (K)
Size Class: sub-Neptune-size
Mass Class:
Detection Type : Primary Transit
Mass Detection :
Radius Detection :
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : Kepler-121
Alternate Name : "2MASS J19043889+3940407, KIC 4545187, KOI-223, WISE J190438.90+394040.9"
Star Distance(LY) : 1664.7
Stellar Radius(Rsun) : 0.7 (Rsun Measured)
Stellar Mass(Msun) : 0.6 (Msun Measured) 0.8 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 5311 (K)
Spectral type : K0
UV portion[%]: 5.9
Visible portion[%]: 41.5
IR portion[%]: 52.6
Metalicity : -0.4
Absolute Magnitude: 4.8
Apparent Magnitude: 13.3
Right Ascension(RA) 286.1621
Declination (DEC) 39.6780
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors 0
Discovery Paper - Title
Discovery Paper - Journal 0
Discovery Paper - URL 0
SIMBAD LINK http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Kepler-121+&submit=SIMBAD+search
Open Exoplanet Database Link http://www.openexoplanetcatalogue.com/planet/Kepler-121%20b/
Kepler-121 b
Kepler-121 b

  • Kepler-121 b is an exoplanet orbiting the star Kepler-121, located about 1664.7 light-years (510.4 pc) away from Solar System. Its discovery was publicly announced on 2014.
  • The host star Kepler-121 has apparent magnitude of 13.3, with absolute magnitude of 4.8.
  • It is 0.6 times more massive and 0.7 times bigger compared with our Sun. The surface temperature is 5311 with its spectral types of K0
  • In this planetary system, the extrasolar planet Kepler-121 b orbits around the star Kepler-121 every 3.2 days with its orbital distance of 0.04 AU ( 5834317.0 km)
  • (Projected orbit of Kepler-121 b around its host star Kepler-121)


  • The Star Kepler-121 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.419 AU ( 62618302.0 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.579 AU ( 86554857.5 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.882 AU ( 131890448.2 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 1.297 AU ( 194082572.3 km)
  • Radiation at Planetary Boundary of Kepler-121 b : 300996.85 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star Kepler-121)



  • Kopparapu Recent Venus for Star Kepler-121 distance : 0.446 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star Kepler-121 distance : 0.564 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star Kepler-121 distance : 0.545 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star Kepler-121 distance : 0.598 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star Kepler-121 distance : 1.011 AU
  • Kopparapu Outer Boundary for Early Mars for Star Kepler-121 distance : 1.066 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star Kepler-121)



  • Original Kopparapu Recent Venus for Star Kepler-121 distance : 0.443 AU
  • Original Kopparapu Runaway Greenhouse for Star Kepler-121 distance : 0.581 AU
  • Original Kopparapu Moist Greenhouse for Star Kepler-121 distance : 0.586 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star Kepler-121 distance : 1.028 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star Kepler-121 distance : 1.069 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star Kepler-121)



    (Position in Stellar Map of star Kepler-121 and its Exoplanet Kepler-121 b)



    (Zoomed position in Stellar Map of star Kepler-121 and its Exoplanet Kepler-121 b (zoom level 3))

    (Synthetic Spectrum of star Kepler-121*)
    *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