Imaginary Picture of K2-255 b

Display orbital revolution of K2-255 b around the hoststar K2-255
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Exoplanet Name : K2-255 b
Alternate Name : "2MASS J12393912-0322138 b, EPIC 228894622 b, EPIC 228894622.01, WISE J123939.09-032213.9 b"
Status : Confirmed
Radius (Rjup / Re): 0.2590 (Rjup) 2.9031 (Rearth)
Mass (Mjup / Me): 0.0224 (Mjup) 7.1085 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0274 (AU) 0.0274 (AU Est.)
Eccentricity : 0.0000
Orbital Period(Yrs) 0.0054
Orbital Period(Observed/Estimated) 1.96 (Days Obs.) 1.97 (Days Est.)
Surface Gravity (G Earth) 0.8434
Star Radiation at Atmospheric Boundary: 371791.9 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 1102.1 (K)
Blackbody T 0.3(K) 1035.0 (K)
Blackbody T 0.7(K) 837.4 (K)
Tidally Locked Blackbody T 0.1(K) 1310.6 (K)
Tidally Locked Blackbody T 0.3(K) 1230.8 (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 : K2-255
Alternate Name : "2MASS J12393912-0322138, EPIC 228894622, WISE J123939.09-032213.9"
Star Distance(LY) : 624.5
Stellar Radius(Rsun) : 0.7 (Rsun Measured)
Stellar Mass(Msun) : 0.7 (Msun Measured) 0.7 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 4676 (K)
Spectral type : K4
UV portion[%]: 2.1
Visible portion[%]: 33.8
IR portion[%]: 64.0
Metalicity : -0.1
Absolute Magnitude: 5.1
Apparent Magnitude: 11.6
Right Ascension(RA) 189.9130
Declination (DEC) -3.3705
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors
Discovery Paper - Title
Discovery Paper - Journal
Discovery Paper - URL
SIMBAD LINK https://simbad.u-strasbg.fr/simbad/sim-basic?Ident=K2-255&submit=SIMBAD+search
Open Exoplanet Database Link
K2-255 b
K2-255 b

  • K2-255 b is an exoplanet orbiting the star K2-255, located about 624.5 light-years (191.5 pc) away from Solar System. Its discovery was publicly announced on 2018.
  • The host star K2-255 has apparent magnitude of 11.6, with absolute magnitude of 5.1.
  • It is 0.7 times more massive and 0.7 times bigger compared with our Sun. The surface temperature is 4676 with its spectral types of K4
  • In this planetary system, the extrasolar planet K2-255 b orbits around the star K2-255 every 2.0 days with its orbital distance of 0.03 AU ( 4098981.7 km)
  • (Projected orbit of K2-255 b around its host star K2-255)


  • The Star K2-255 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.327 AU ( 48894072.1 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.452 AU ( 67584385.1 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.688 AU ( 102983646.5 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 1.013 AU ( 151544947.3 km)
  • Radiation at Planetary Boundary of K2-255 b : 371791.86 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star K2-255)



  • Kopparapu Recent Venus for Star K2-255 distance : 0.359 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-255 distance : 0.454 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-255 distance : 0.439 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-255 distance : 0.481 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-255 distance : 0.834 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-255 distance : 0.880 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star K2-255)



  • Original Kopparapu Recent Venus for Star K2-255 distance : 0.354 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-255 distance : 0.468 AU
  • Original Kopparapu Moist Greenhouse for Star K2-255 distance : 0.468 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-255 distance : 0.848 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-255 distance : 0.882 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star K2-255)



    (Position in Stellar Map of star K2-255 and its Exoplanet K2-255 b)



    (Zoomed position in Stellar Map of star K2-255 and its Exoplanet K2-255 b (zoom level 3))

    (Synthetic Spectrum of star K2-255*)
    *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