Imaginary Picture of K2-128 b

Display orbital revolution of K2-128 b around the hoststar K2-128
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Exoplanet Name : K2-128 b
Alternate Name : "EPIC 212686205 b, 2MASS J13374504-0835494 b, EPIC 212686205.01, WISE J133745.03-083549.4 b"
Status : Confirmed
Radius (Rjup / Re): 0.1270 (Rjup) 1.4235 (Rearth)
Mass (Mjup / Me): 0.0111 (Mjup) 3.5132 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0560 (AU) 0.0560 (AU Est.)
Eccentricity : 0.2300
Orbital Period(Yrs) 0.0155
Orbital Period(Observed/Estimated) 5.68 (Days Obs.) 5.74 (Days Est.)
Surface Gravity (G Earth) 1.7337
Star Radiation at Atmospheric Boundary: 94898.5 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 783.4 (K)
Blackbody T 0.3(K) 735.7 (K)
Blackbody T 0.7(K) 595.2 (K)
Tidally Locked Blackbody T 0.1(K) 931.6 (K)
Tidally Locked Blackbody T 0.3(K) 874.8 (K)
Size Class: super-Earth-size
Mass Class:
Detection Type : Primary Transit
Mass Detection :
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : K2-128
Alternate Name : "EPIC 212686205, 2MASS J13374504-0835494, WISE J133745.03-083549.4"
Star Distance(LY) : 375.1
Stellar Radius(Rsun) : 0.8 (Rsun Measured)
Stellar Mass(Msun) : 0.7 (Msun Measured) 0.7 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 4469 (K)
Spectral type : K4V
UV portion[%]: 1.5
Visible portion[%]: 30.6
IR portion[%]: 67.9
Metalicity : 0.0
Absolute Magnitude: 5.2
Apparent Magnitude: 10.5
Right Ascension(RA) 204.4377
Declination (DEC) -8.5971
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=K2-128+&submit=SIMBAD+search
Open Exoplanet Database Link
K2-128 b
K2-128 b

  • K2-128 b is an exoplanet orbiting the star K2-128, located about 375.1 light-years (115.0 pc) away from Solar System. Its discovery was publicly announced on 2017.
  • The host star K2-128 has apparent magnitude of 10.5, with absolute magnitude of 5.2.
  • It is 0.7 times more massive and 0.8 times bigger compared with our Sun. The surface temperature is 4469 with its spectral types of K4V
  • In this planetary system, the extrasolar planet K2-128 b orbits around the star K2-128 every 5.7 days with its orbital distance of 0.06 AU ( 8377480.8 km)
  • (Projected orbit of K2-128 b around its host star K2-128)


  • The Star K2-128 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.337 AU ( 50486286.1 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.466 AU ( 69785241.1 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.711 AU ( 106337264.0 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 1.046 AU ( 156479942.3 km)
  • Radiation at Planetary Boundary of K2-128 b : 94898.51 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star K2-128)



  • Kopparapu Recent Venus for Star K2-128 distance : 0.373 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-128 distance : 0.472 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-128 distance : 0.456 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-128 distance : 0.501 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-128 distance : 0.876 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-128 distance : 0.924 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star K2-128)



  • Original Kopparapu Recent Venus for Star K2-128 distance : 0.368 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-128 distance : 0.488 AU
  • Original Kopparapu Moist Greenhouse for Star K2-128 distance : 0.487 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-128 distance : 0.890 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-128 distance : 0.926 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star K2-128)



    (Position in Stellar Map of star K2-128 and its Exoplanet K2-128 b)



    (Zoomed position in Stellar Map of star K2-128 and its Exoplanet K2-128 b (zoom level 3))

    (Synthetic Spectrum of star K2-128*)
    *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