Imaginary Picture of HD 20781 b

Display orbital revolution of HD 20781 b around the hoststar HD 20781
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Exoplanet Name : HD 20781 b
Alternate Name :
Status : Confirmed
Radius (Rjup / Re): 0.2052 (Rjup) 2.2998 (Rearth)
Mass (Mjup / Me): 0.0379 (Mjup) 12.0499 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.1690 (AU) 0.1690 (AU Est.)
Eccentricity : 0.1100
Orbital Period(Yrs) 0.0798
Orbital Period(Observed/Estimated) 29.15 (Days Obs.) 23.97 (Days Est.)
Surface Gravity (G Earth) 2.2782
Star Radiation at Atmospheric Boundary: 47856.6 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 660.1 (K)
Blackbody T 0.3(K) 619.9 (K)
Blackbody T 0.7(K) 501.6 (K)
Tidally Locked Blackbody T 0.1(K) 785.0 (K)
Tidally Locked Blackbody T 0.3(K) 737.2 (K)
Size Class: sub-Neptune-size
Mass Class:
Detection Type : Radial Velocity
Mass Detection :
Radius Detection :
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : HD 20781
Alternate Name :
Star Distance(LY) : 116.7
Stellar Radius(Rsun) : 1.1 (Rsun Estimated)
Stellar Mass(Msun) : 1.1 (Msun Measured) 0.8 (Msun Estimated)
Star Age : 0.0 (GY)
Temperature : 5500 (K)
Spectral type : G9.5V
UV portion[%]: 6.9
Visible portion[%]: 43.2
IR portion[%]: 49.9
Metalicity : 0.0
Absolute Magnitude: 5.7
Apparent Magnitude: 8.4
Right Ascension(RA) 50.0123
Declination (DEC) -28.7839
Hubble Space Telescope Guide Star Catalog (GSC) ID 06445-00983
Discovered by
Discovery Paper - Authors "S. Desidera, M. Barbieri"
Discovery Paper - Title Properties of planets in binary systems. The role of binary separation
Discovery Paper - Journal 0
Discovery Paper - URL 0
SIMBAD LINK http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+20781+&submit=SIMBAD+search
Open Exoplanet Database Link http://www.openexoplanetcatalogue.com/planet/HD%2020781%20b/
HD 20781 b
HD 20781 b

  • HD 20781 b is an exoplanet orbiting the star HD 20781, located about 116.7 light-years (35.8 pc) away from Solar System. Its discovery was publicly announced on 2011.
  • The host star HD 20781 has apparent magnitude of 8.4, with absolute magnitude of 5.7.
  • It is 1.1 times more massive and 1.1 times bigger compared with our Sun. The surface temperature is 5500 with its spectral types of G9.5V
  • In this planetary system, the extrasolar planet HD 20781 b orbits around the star HD 20781 every 29.1 days with its orbital distance of 0.17 AU ( 25282040.1 km)
  • (Projected orbit of HD 20781 b around its host star HD 20781)


  • The Star HD 20781 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.723 AU ( 108196493.8 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 1.000 AU ( 149555829.6 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 1.523 AU ( 227889987.7 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 2.242 AU ( 335350100.1 km)
  • Radiation at Planetary Boundary of HD 20781 b : 47856.57 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star HD 20781)



  • Kopparapu Recent Venus for Star HD 20781 distance : 0.762 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star HD 20781 distance : 0.965 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star HD 20781 distance : 0.932 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star HD 20781 distance : 1.022 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star HD 20781 distance : 1.718 AU
  • Kopparapu Outer Boundary for Early Mars for Star HD 20781 distance : 1.812 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star HD 20781)



  • Original Kopparapu Recent Venus for Star HD 20781 distance : 0.759 AU
  • Original Kopparapu Runaway Greenhouse for Star HD 20781 distance : 0.992 AU
  • Original Kopparapu Moist Greenhouse for Star HD 20781 distance : 1.004 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star HD 20781 distance : 1.747 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star HD 20781 distance : 1.817 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star HD 20781)



    (Position in Stellar Map of star HD 20781 and its Exoplanet HD 20781 b)



    (Zoomed position in Stellar Map of star HD 20781 and its Exoplanet HD 20781 b (zoom level 3))

    (Synthetic Spectrum of star HD 20781*)
    *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