Imaginary Picture of K2-399 b

Display orbital revolution of K2-399 b around the hoststar K2-399
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Exoplanet Name : K2-399 b
Alternate Name : "TOI-4838 b, TOI-4838.01"
Status : Confirmed
Radius (Rjup / Re): 0.5397 (Rjup) 6.0490 (Rearth)
Mass (Mjup / Me): 0.1016 (Mjup) 32.2898 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0163 (AU) 0.0163 (AU Est.)
Eccentricity : 0.0000
Orbital Period(Yrs) 0.0021
Orbital Period(Observed/Estimated) 0.76 (Days Obs.) 0.76 (Days Est.)
Surface Gravity (G Earth) 0.8825
Star Radiation at Atmospheric Boundary: 13250569.3 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 2692.8 (K)
Blackbody T 0.3(K) 2528.8 (K)
Blackbody T 0.7(K) 2046.1 (K)
Tidally Locked Blackbody T 0.1(K) 3202.3 (K)
Tidally Locked Blackbody T 0.3(K) 3007.3 (K)
Size Class: sub-Jupiter-size
Mass Class:
Detection Type : Primary Transit
Mass Detection : Spectrum
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : K2-399
Alternate Name : "EPIC 248472140, TOI-4838"
Star Distance(LY) : 1681.3
Stellar Radius(Rsun) : 1.7 (Rsun Measured)
Stellar Mass(Msun) : 1.0 (Msun Measured) 1.0 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 5690 (K)
Spectral type : G2IV
UV portion[%]: 7.6
Visible portion[%]: 44.4
IR portion[%]: 48.1
Metalicity : 0.3
Absolute Magnitude: 3.9
Apparent Magnitude: 12.5
Right Ascension(RA) 158.0735
Declination (DEC) 2.2379
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
K2-399 b
K2-399 b

  • K2-399 b is an exoplanet orbiting the star K2-399, located about 1681.3 light-years (515.5 pc) away from Solar System. Its discovery was publicly announced on 2022.
  • The host star K2-399 has apparent magnitude of 12.5, with absolute magnitude of 3.9.
  • It is 1.0 times more massive and 1.7 times bigger compared with our Sun. The surface temperature is 5690 with its spectral types of G2IV
  • In this planetary system, the extrasolar planet K2-399 b orbits around the star K2-399 every 0.8 days with its orbital distance of 0.02 AU ( 2445925.2 km)
  • (Projected orbit of K2-399 b around its host star K2-399)


  • The Star K2-399 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 1.164 AU ( 174176970.8 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 1.609 AU ( 240758091.6 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 2.452 AU ( 366862051.9 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 3.609 AU ( 539853580.5 km)
  • Radiation at Planetary Boundary of K2-399 b : 13250569.31 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star K2-399)



  • Kopparapu Recent Venus for Star K2-399 distance : 1.213 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-399 distance : 1.536 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-399 distance : 1.484 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-399 distance : 1.627 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-399 distance : 2.719 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-399 distance : 2.868 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star K2-399)



  • Original Kopparapu Recent Venus for Star K2-399 distance : 1.213 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-399 distance : 1.579 AU
  • Original Kopparapu Moist Greenhouse for Star K2-399 distance : 1.604 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-399 distance : 2.767 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-399 distance : 2.877 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star K2-399)



    (Position in Stellar Map of star K2-399 and its Exoplanet K2-399 b)



    (Zoomed position in Stellar Map of star K2-399 and its Exoplanet K2-399 b (zoom level 3))

    (Synthetic Spectrum of star K2-399*)
    *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