Imaginary Picture of BD-21 397 b

Display orbital revolution of BD-21 397 b around the hoststar BD-21 397
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Exoplanet Name : BD-21 397 b
Alternate Name :
Status : Confirmed
Radius (Rjup / Re): 0.9078 (Rjup) 10.1759 (Rearth)
Mass (Mjup / Me): 0.7000 (Mjup) 222.5566 (Mearth)
Semi Major Axis / Orbital Distance Calculated 2.6300 (AU) 2.6300 (AU Est.)
Eccentricity : 0.1000
Orbital Period(Yrs) 5.1771
Orbital Period(Observed/Estimated) 1891.00 (Days Obs.) 1890.55 (Days Est.)
Surface Gravity (G Earth) 2.1493
Star Radiation at Atmospheric Boundary: 26.6 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 101.4 (K)
Blackbody T 0.3(K) 95.2 (K)
Blackbody T 0.7(K) 77.0 (K)
Tidally Locked Blackbody T 0.1(K) 120.6 (K)
Tidally Locked Blackbody T 0.3(K) 113.2 (K)
Size Class: Jupiter-size
Mass Class:
Detection Type : Radial Velocity
Mass Detection : Radial Velocity
Radius Detection :
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : BD-21 397
Alternate Name :
Star Distance(LY) : 77.4
Stellar Radius(Rsun) : 0.7 (Rsun Measured)
Stellar Mass(Msun) : 0.7 (Msun Measured) 0.7 (Msun Estimated)
Star Age : 6.2 (GY)
Temperature : 4051 (K)
Spectral type : K7V
UV portion[%]: 0.7
Visible portion[%]: 24.6
IR portion[%]: 74.7
Metalicity : 0.1
Absolute Magnitude: 7.9
Apparent Magnitude: 9.8
Right Ascension(RA) 33.3000
Declination (DEC) -21.1964
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
BD-21 397 b
BD-21 397 b

  • BD-21 397 b is an exoplanet orbiting the star BD-21 397, located about 77.4 light-years (23.7 pc) away from Solar System. Its discovery was publicly announced on 2023.
  • The host star BD-21 397 has apparent magnitude of 9.8, with absolute magnitude of 7.9.
  • It is 0.7 times more massive and 0.7 times bigger compared with our Sun. The surface temperature is 4051 with its spectral types of K7V
  • In this planetary system, the extrasolar planet BD-21 397 b orbits around the star BD-21 397 every 1891.0 days with its orbital distance of 2.63 AU ( 393442399.9 km)
  • (Projected orbit of BD-21 397 b around its host star BD-21 397)


  • The Star BD-21 397 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 0.266 AU ( 39728594.5 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 0.367 AU ( 54915299.9 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 0.559 AU ( 83678764.3 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 0.823 AU ( 123136967.4 km)
  • Radiation at Planetary Boundary of BD-21 397 b : 26.64 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star BD-21 397)



  • Kopparapu Recent Venus for Star BD-21 397 distance : 0.297 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star BD-21 397 distance : 0.376 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star BD-21 397 distance : 0.363 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star BD-21 397 distance : 0.399 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star BD-21 397 distance : 0.712 AU
  • Kopparapu Outer Boundary for Early Mars for Star BD-21 397 distance : 0.751 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star BD-21 397)



  • Original Kopparapu Recent Venus for Star BD-21 397 distance : 0.293 AU
  • Original Kopparapu Runaway Greenhouse for Star BD-21 397 distance : 0.389 AU
  • Original Kopparapu Moist Greenhouse for Star BD-21 397 distance : 0.388 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star BD-21 397 distance : 0.723 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star BD-21 397 distance : 0.752 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star BD-21 397)



    (Position in Stellar Map of star BD-21 397 and its Exoplanet BD-21 397 b)



    (Zoomed position in Stellar Map of star BD-21 397 and its Exoplanet BD-21 397 b (zoom level 3))

    (Synthetic Spectrum of star BD-21 397*)
    *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