Imaginary Picture of HATS-21 b

Display orbital revolution of HATS-21 b around the hoststar HATS-21
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Exoplanet Name : HATS-21 b
Alternate Name :
Status : Confirmed
Radius (Rjup / Re): 1.1230 (Rjup) 12.5877 (Rearth)
Mass (Mjup / Me): 0.3320 (Mjup) 105.5554 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0468 (AU) 0.0468 (AU Est.)
Eccentricity : 0.0000
Orbital Period(Yrs) 0.0097
Orbital Period(Observed/Estimated) 3.55 (Days Obs.) 3.55 (Days Est.)
Surface Gravity (G Earth) 0.6662
Star Radiation at Atmospheric Boundary: 615010.0 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 1249.9 (K)
Blackbody T 0.3(K) 1173.8 (K)
Blackbody T 0.7(K) 949.7 (K)
Tidally Locked Blackbody T 0.1(K) 1486.3 (K)
Tidally Locked Blackbody T 0.3(K) 1395.8 (K)
Size Class: 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 : HATS-21
Alternate Name :
Star Distance(LY) : 932.8
Stellar Radius(Rsun) : 1.0 (Rsun Measured)
Stellar Mass(Msun) : 1.1 (Msun Measured) 1.1 (Msun Estimated)
Star Age : 2.3 (GY)
Temperature : 5695 (K)
Spectral type : G4V
UV portion[%]: 7.6
Visible portion[%]: 44.4
IR portion[%]: 48.0
Metalicity : 0.3
Absolute Magnitude: 4.9
Apparent Magnitude: 12.2
Right Ascension(RA) 280.1833
Declination (DEC) -58.4592
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors
Discovery Paper - Title
Discovery Paper - Journal 0
Discovery Paper - URL 0
SIMBAD LINK
Open Exoplanet Database Link
HATS-21 b
HATS-21 b

  • HATS-21 b is an exoplanet orbiting the star HATS-21, located about 932.8 light-years (286.0 pc) away from Solar System. Its discovery was publicly announced on 2016.
  • The host star HATS-21 has apparent magnitude of 12.2, with absolute magnitude of 4.9.
  • It is 1.1 times more massive and 1.0 times bigger compared with our Sun. The surface temperature is 5695 with its spectral types of G4V
  • In this planetary system, the extrasolar planet HATS-21 b orbits around the star HATS-21 every 3.6 days with its orbital distance of 0.05 AU ( 6995196.4 km)
  • (Projected orbit of HATS-21 b around its host star HATS-21)


  • The Star HATS-21 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.717 AU ( 107317688.9 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.992 AU ( 148341091.5 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 1.511 AU ( 226038995.6 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 2.223 AU ( 332626284.2 km)
  • Radiation at Planetary Boundary of HATS-21 b : 615010.04 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star HATS-21)



  • Kopparapu Recent Venus for Star HATS-21 distance : 0.747 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star HATS-21 distance : 0.946 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star HATS-21 distance : 0.914 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star HATS-21 distance : 1.002 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star HATS-21 distance : 1.675 AU
  • Kopparapu Outer Boundary for Early Mars for Star HATS-21 distance : 1.766 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star HATS-21)



  • Original Kopparapu Recent Venus for Star HATS-21 distance : 0.747 AU
  • Original Kopparapu Runaway Greenhouse for Star HATS-21 distance : 0.973 AU
  • Original Kopparapu Moist Greenhouse for Star HATS-21 distance : 0.988 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star HATS-21 distance : 1.704 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star HATS-21 distance : 1.772 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star HATS-21)



    (Position in Stellar Map of star HATS-21 and its Exoplanet HATS-21 b)



    (Zoomed position in Stellar Map of star HATS-21 and its Exoplanet HATS-21 b (zoom level 3))

    (Synthetic Spectrum of star HATS-21*)
    *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