Imaginary Picture of K2-18 b

Display orbital revolution of K2-18 b around the hoststar K2-18
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Exoplanet Name : K2-18 b
Alternate Name : "EPIC 201912552 b, 2MASS J11301450+0735180 b, EPIC 201912552.01, WISE J113014.45+073516.8 b"
Status : Confirmed
Radius (Rjup / Re): 0.2110 (Rjup) 2.3651 (Rearth)
Mass (Mjup / Me): 0.0281 (Mjup) 8.9245 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.1429 (AU) 0.1429 (AU Est.)
Eccentricity : 0.2000
Orbital Period(Yrs) 0.0902
Orbital Period(Observed/Estimated) 32.94 (Days Obs.) 32.88 (Days Est.)
Surface Gravity (G Earth) 1.5955
Star Radiation at Atmospheric Boundary: 1441.8 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 275.0 (K)
Blackbody T 0.3(K) 258.3 (K)
Blackbody T 0.7(K) 209.0 (K)
Tidally Locked Blackbody T 0.1(K) 327.1 (K)
Tidally Locked Blackbody T 0.3(K) 307.1 (K)
Size Class: sub-Neptune-size
Mass Class:
Detection Type : Primary Transit
Mass Detection : Theoretical
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Habitable
Habitability by Kopparapu: Not habitable
Star Name : K2-18
Alternate Name : "EPIC 201912552, 2MASS J11301450+0735180, WISE J113014.45+073516.8"
Star Distance(LY) : 124.2
Stellar Radius(Rsun) : 0.4 (Rsun Measured)
Stellar Mass(Msun) : 0.4 (Msun Measured) 0.4 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 3457 (K)
Spectral type : M2.5 V
UV portion[%]: 0.3
Visible portion[%]: 13.3
IR portion[%]: 86.4
Metalicity : 0.1
Absolute Magnitude: 10.6
Apparent Magnitude: 13.5
Right Ascension(RA) 172.5605
Declination (DEC) 7.5884
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=K2-18+&submit=SIMBAD+search
Open Exoplanet Database Link
K2-18 b
K2-18 b

  • K2-18 b is an exoplanet orbiting the star K2-18, located about 124.2 light-years (38.1 pc) away from Solar System. Its discovery was publicly announced on 2015.
  • The host star K2-18 has apparent magnitude of 13.5, with absolute magnitude of 10.6.
  • It is 0.4 times more massive and 0.4 times bigger compared with our Sun. The surface temperature is 3457 with its spectral types of M2.5 V
  • In this planetary system, the extrasolar planet K2-18 b orbits around the star K2-18 every 32.9 days with its orbital distance of 0.14 AU ( 21377535.7 km)
  • (Projected orbit of K2-18 b around its host star K2-18)


  • The Star K2-18 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.106 AU ( 15879642.8 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.147 AU ( 21949816.2 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.224 AU ( 33446662.3 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 0.329 AU ( 49218228.8 km)
  • Radiation at Planetary Boundary of K2-18 b : 1441.80 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star K2-18)



  • Kopparapu Recent Venus for Star K2-18 distance : 0.120 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-18 distance : 0.152 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-18 distance : 0.147 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-18 distance : 0.161 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-18 distance : 0.296 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-18 distance : 0.312 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star K2-18)



  • Original Kopparapu Recent Venus for Star K2-18 distance : 0.119 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-18 distance : 0.157 AU
  • Original Kopparapu Moist Greenhouse for Star K2-18 distance : 0.158 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-18 distance : 0.301 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-18 distance : 0.313 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star K2-18)



    (Position in Stellar Map of star K2-18 and its Exoplanet K2-18 b)



    (Zoomed position in Stellar Map of star K2-18 and its Exoplanet K2-18 b (zoom level 3))

    (Synthetic Spectrum of star K2-18*)
    *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