Imaginary Picture of K2-18 b
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Exoplanet Name : K2-18 b
Alternate Name : EPIC 201912552 b
Radius (Rjup / Re): 0.2000 (Rjup) 2.2418 (Rearth)
Mass (Mjup / Me): 0.0250 (Mjup) 7.9485 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.1430 (AU) 0.1430 (AU Est.)
Eccentricity : 0.4300
Orbital Period(Yrs) 0.0902
Orbital Period(Observed/Estimated) 32.94 (Days Obs.) 30.73 (Days Est.)
Star Radiation at Atmospheric Boundary: 1401.8 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 273.1 (K)
Blackbody T 0.3(K) 256.5 (K)
Blackbody T 0.7(K) 207.5 (K)
Tidally Locked Blackbody T 0.1(K) 324.8 (K)
Tidally Locked Blackbody T 0.3(K) 305.0 (K)
Size Class: sub-Neptune-size
Mass Class:
Detection Type : Primary Transit
Mass Detection : Radial Velocity
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Habitable
Habitability by Kopparapu: Not habitable
Star Name : K2-18
Alternate Name : EPIC 201912552
Star Distance(LY) : 110.9
Stellar Radius(Rsun) : 0.4 (Rsun Measured)
Stellar Mass(Msun) : 0.4 (Msun Measured) 0.4 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 3503 (K)
Spectral type : M4
Metalicity : 0.1
Absolute Magnitude: 19.3
Apparent Magnitude: 22.0
Right Ascension(RA) 172.5605
Declination (DEC) 7.5884
Hubble Space Telescope Guide Star Catalog (GSC) ID 0
Discovered by
Discovery Paper - Authors "Benjamin T. Montet, Timothy D. Morton, Daniel Foreman-Mackey, John Asher Johnson, David W. Hogg, Brendan P. Bowler, David W. Latham, Allyson Bieryla, Andrew W. Mann"
Discovery Paper - Title "STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 18 SYSTEMS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION "
Discovery Paper - Journal 0
Discovery Paper - URL https://arxiv.org/pdf/1503.07866v1.pdf
SIMBAD LINK http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=K2-18+&submit=SIMBAD+search
Open Exoplanet Database Link http://www.openexoplanetcatalogue.com/planet/EPIC%20201912552%20b/
K2-18 b
K2-18 b

  • K2-18 b is an exoplanet orbiting the star K2-18, located about 110.9 light-years (34.0 pc) away from Solar System. Its discovery was publicly announced on 2015.
  • The host star K2-18 has apparent magnitude of 22.0, with absolute magnitude of 19.3.
  • It is 0.4 times more massive and 0.4 times bigger compared with our Sun. The surface temperature is 3503 with its spectral types of M4
  • 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 ( 21392495.5 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 ) : 0.105 AU ( 15668759.3 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.145 AU ( 21658320.1 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.221 AU ( 33002486.8 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 0.325 AU ( 48564605.1 km)
  • Radiation at Planetary Boundary of K2-18 b : 1401.80 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 : 0.118 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-18 distance : 0.150 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-18 distance : 0.145 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-18 distance : 0.159 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-18 distance : 0.291 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-18 distance : 0.307 AU

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



  • Original Kopparapu Recent Venus for Star K2-18 distance : 0.117 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-18 distance : 0.155 AU
  • Original Kopparapu Moist Greenhouse for Star K2-18 distance : 0.155 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-18 distance : 0.296 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-18 distance : 0.308 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))