Imaginary Picture of Kepler-21 A b

Display orbital revolution of Kepler-21 A b around the hoststar Kepler-21 A
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Exoplanet Name : Kepler-21 A b
Alternate Name : Kepler-21 b
Radius (Rjup / Re): 0.1462 (Rjup) 1.6388 (Rearth)
Mass (Mjup / Me): 0.0160 (Mjup) 5.0870 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.0427 (AU) 0.0427 (AU Est.)
Eccentricity : 0.0200
Orbital Period(Yrs) 0.0076
Orbital Period(Observed/Estimated) 2.79 (Days Obs.) 2.79 (Days Est.)
Surface Gravity (G Earth) 1.8942
Star Radiation at Atmospheric Boundary: 3285113.7 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 1900.1 (K)
Blackbody T 0.3(K) 1784.4 (K)
Blackbody T 0.7(K) 1443.8 (K)
Tidally Locked Blackbody T 0.1(K) 2259.6 (K)
Tidally Locked Blackbody T 0.3(K) 2122.0 (K)
Size Class: super-Earth-size
Mass Class:
Detection Type : Primary Transit
Mass Detection :
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : Kepler-21 A
Alternate Name : Kepler-21
Star Distance(LY) : 352.2
Stellar Radius(Rsun) : 1.9 (Rsun Measured)
Stellar Mass(Msun) : 1.3 (Msun Measured) 1.3 (Msun Estimated)
Star Age : 2.8 (GY)
Temperature : 6131 (K)
Spectral type : F6IV
UV portion[%]: 7.8
Visible portion[%]: 44.8
IR portion[%]: 47.4
Metalicity : -0.1
Absolute Magnitude: 3.1
Apparent Magnitude: 8.3
Right Ascension(RA) 287.3618
Declination (DEC) 38.7139
Hubble Space Telescope Guide Star Catalog (GSC) ID 03120-00963
Discovered by
Discovery Paper - Authors "Howell,teve.; Rowe,ason.; Bryson,tephen.; Quinn,amuel.; Marcy,eoffrey.; Isaacson,oward; Ciardi,avid.; Chaplin,illiam.; Metcalfe,ravis.; Monteiro,ario....; Appourchaux,hierry; Basu,arbani; Creevey,rlagh.; Gilliland,onald.; Quirion,ierre-Olivier; Stello,enis; Kjeldsen,ans; Christensen-Dalsgaard,_rgen; Elsworth,vonne; Garc_a,afael.; Houdek,_nter; Karoff,hristoffer; Molenda-_akowicz,oanna; Thompson,ichael.; Verner,raham.; Torres,uillermo; Fressin,rancois; Crepp,ustin.; Adams,lisabeth; Dupree,ndrea; Sasselov,imitar.; Dressing,ourtney.; Borucki,illiam.; Koch,avid.; Lissauer,ack.; Latham,avid.; Buchhave,ars.; Gautier,homas.,II; Everett,ark; Horch,lliott; Batalha,atalie.; Dunham,dward.; Szkody,aula; Silva,avid.; Mighell,en; Holberg,ay; Ballot,er_me; Bedding,imothy.; Bruntt,ans; Campante,iago.; Handberg,asmus; Hekker,askia; Huber,aniel; Mathur,avita; Mosser,enoit; R_gulo,lara; White,imothy.; Christiansen,essie.; Middour,hristopher.; Haas,ichael.; Hall,ennifer.; Jenkins,on.; McCaulif,ean; Fanelli,ichael.; Kulesa,raig; McCarthy,on; Henze,hristopher."
Discovery Paper - Title Kepler-21b: A 1.6 R Earth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070
Discovery Paper - Journal 0
Discovery Paper - URL 0
SIMBAD LINK http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Kepler-21+&submit=SIMBAD+search
Open Exoplanet Database Link http://www.openexoplanetcatalogue.com/planet/Kepler-21%20b/
Kepler-21 A b
Kepler-21 A b
  • Kepler-21 A b is an exoplanet orbiting the star Kepler-21 A, located about 352.2 light-years (108.0 pc) away from Solar System. Its discovery was publicly announced on 2011.
  • The host star Kepler-21 A has apparent magnitude of 8.3, with absolute magnitude of 3.1.
  • It is 1.3 times more massive and 1.9 times bigger compared with our Sun. The surface temperature is 6131 with its spectral types of F6IV
  • In this planetary system, the extrasolar planet Kepler-21 A b orbits around the star Kepler-21 A every 2.8 days with its orbital distance of 0.04 AU ( 6390402.2 km)
    • (Projected orbit of Kepler-21 A b around its host star Kepler-21 A)


  • The Star Kepler-21 A 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 1.515 AU ( 226586321.5 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 2.094 AU ( 313201510.4 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 3.190 AU ( 477249790.5 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 4.695 AU ( 702293973.7 km)
  • Radiation at Planetary Boundary of Kepler-21 A b : 3285113.71 W/m2

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



  • Kopparapu Recent Venus for Star Kepler-21 A distance : 1.537 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star Kepler-21 A distance : 1.946 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star Kepler-21 A distance : 1.879 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star Kepler-21 A distance : 2.060 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star Kepler-21 A distance : 3.408 AU
  • Kopparapu Outer Boundary for Early Mars for Star Kepler-21 A distance : 3.594 AU

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



  • Original Kopparapu Recent Venus for Star Kepler-21 A distance : 1.550 AU
  • Original Kopparapu Runaway Greenhouse for Star Kepler-21 A distance : 1.997 AU
  • Original Kopparapu Moist Greenhouse for Star Kepler-21 A distance : 2.051 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star Kepler-21 A distance : 3.468 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star Kepler-21 A distance : 3.607 AU

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



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



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