Imaginary Picture of K2-309 c

Display orbital revolution of K2-309 c around the hoststar K2-309
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Exoplanet Name : K2-309 c
Alternate Name : *V1298 Tau c
Status : Confirmed
Radius (Rjup / Re): 0.4675 (Rjup) 5.2402 (Rearth)
Mass (Mjup / Me): 0.0623 (Mjup) 19.8075 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0839 (AU) 0.0839 (AU Est.)
Eccentricity : 0.4300
Orbital Period(Yrs) 0.0226
Orbital Period(Observed/Estimated) 8.25 (Days Obs.) 8.46 (Days Est.)
Surface Gravity (G Earth) 0.7213
Star Radiation at Atmospheric Boundary: 181020.4 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 920.6 (K)
Blackbody T 0.3(K) 864.5 (K)
Blackbody T 0.7(K) 699.5 (K)
Tidally Locked Blackbody T 0.1(K) 1094.8 (K)
Tidally Locked Blackbody T 0.3(K) 1028.1 (K)
Size Class: sub-Jupiter-size
Mass Class:
Detection Type : Primary Transit
Mass Detection : Radial Velocity
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : K2-309
Alternate Name : *V1298 Tau
Star Distance(LY) : 353.9
Stellar Radius(Rsun) : 1.3 (Rsun Measured)
Stellar Mass(Msun) : 1.1 (Msun Measured) 1.2 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 4970 (K)
Spectral type : K0-K1.5
UV portion[%]: 3.1
Visible portion[%]: 36.8
IR portion[%]: 60.1
Metalicity : 0.0
Absolute Magnitude: 4.9
Apparent Magnitude: 10.1
Right Ascension(RA) 61.3333
Declination (DEC) 20.1572
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
K2-309 c
K2-309 c

  • K2-309 c is an exoplanet orbiting the star K2-309, located about 353.9 light-years (108.5 pc) away from Solar System. Its discovery was publicly announced on 2019.
  • The host star K2-309 has apparent magnitude of 10.1, with absolute magnitude of 4.9.
  • It is 1.1 times more massive and 1.3 times bigger compared with our Sun. The surface temperature is 4970 with its spectral types of K0-K1.5
  • In this planetary system, the extrasolar planet K2-309 c orbits around the star K2-309 every 8.2 days with its orbital distance of 0.08 AU ( 12551261.4 km)
  • (Projected orbit of K2-309 c around its host star K2-309)


  • The Star K2-309 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.698 AU ( 104467548.1 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.965 AU ( 144401452.1 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 1.471 AU ( 220035857.0 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 2.164 AU ( 323792402.7 km)
  • Radiation at Planetary Boundary of K2-309 c : 181020.38 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star K2-309)



  • Kopparapu Recent Venus for Star K2-309 distance : 0.756 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star K2-309 distance : 0.958 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star K2-309 distance : 0.925 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star K2-309 distance : 1.015 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-309 distance : 1.738 AU
  • Kopparapu Outer Boundary for Early Mars for Star K2-309 distance : 1.833 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star K2-309)



  • Original Kopparapu Recent Venus for Star K2-309 distance : 0.748 AU
  • Original Kopparapu Runaway Greenhouse for Star K2-309 distance : 0.987 AU
  • Original Kopparapu Moist Greenhouse for Star K2-309 distance : 0.990 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star K2-309 distance : 1.767 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star K2-309 distance : 1.838 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star K2-309)



    (Position in Stellar Map of star K2-309 and its Exoplanet K2-309 c)



    (Zoomed position in Stellar Map of star K2-309 and its Exoplanet K2-309 c (zoom level 3))

    (Synthetic Spectrum of star K2-309*)
    *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