Imaginary Picture of TOI-257 b
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Exoplanet Name : TOI-257 b
Alternate Name : HD 19916 b
Radius (Rjup / Re): 0.6260 (Rjup) 7.0168 (Rearth)
Mass (Mjup / Me): 0.1340 (Mjup) 42.6037 (Mearth)
Semi Major Axis / Orbital Distance Calculated 0.1523 (AU) 0.1523 (AU Est.)
Eccentricity : 0.2400
Orbital Period(Yrs) 0.0503
Orbital Period(Observed/Estimated) 18.39 (Days Obs.) 18.42 (Days Est.)
Star Radiation at Atmospheric Boundary: 267117.7 (W/m2)
Measured Temperature (K) 0.0 (K)
Blackbody T 0.1(K) 1014.7 (K)
Blackbody T 0.3(K) 952.9 (K)
Blackbody T 0.7(K) 771.0 (K)
Tidally Locked Blackbody T 0.1(K) 1206.6 (K)
Tidally Locked Blackbody T 0.3(K) 1133.2 (K)
Size Class: sub-Jupiter-size
Mass Class:
Detection Type : Primary Transit
Mass Detection : Spectrum
Radius Detection : Primary Transit
Habitability by Solar Eq. Astronomical Unit: Not habitable
Habitability by Kopparapu: Not habitable
Star Name : TOI-257
Alternate Name : HD 19916
Star Distance(LY) : 251.4
Stellar Radius(Rsun) : 1.9 (Rsun Measured)
Stellar Mass(Msun) : 1.4 (Msun Measured) 1.4 (Msun Estimated)
Star Age : 3.1 (GY)
Temperature : 6075 (K)
Spectral type : F8/G0V
Metalicity : 0.2
Absolute Magnitude: 17.6
Apparent Magnitude: 22.0
Right Ascension(RA) 47.5167
Declination (DEC) -50.8325
Hubble Space Telescope Guide Star Catalog (GSC) ID
Discovered by
Discovery Paper - Authors
Discovery Paper - Title
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SIMBAD LINK
Open Exoplanet Database Link
TOI-257 b
TOI-257 b

  • TOI-257 b is an exoplanet orbiting the star TOI-257, located about 251.4 light-years (77.1 pc) away from Solar System. Its discovery was publicly announced on 2020.
  • The host star TOI-257 has apparent magnitude of 22.0, with absolute magnitude of 17.6.
  • It is 1.4 times more massive and 1.9 times bigger compared with our Sun. The surface temperature is 6075 with its spectral types of F8/G0V
  • In this planetary system, the extrasolar planet TOI-257 b orbits around the star TOI-257 every 18.4 days with its orbital distance of 0.15 AU ( 22783755.7 km)
  • (Projected orbit of TOI-257 b around its host star TOI-257)


  • The Star TOI-257 's habitable zone is located at the following distance
  • Inner Boundary (the orbital distance at Venus's Equivalent Radiation ) : 1.540 AU ( 230359941.6 km)
  • Earth Boundary (the orbital distance at Earth's Equivalent Radiation) : 2.128 AU ( 318417639.6 km)
  • Outer Boundary (the orbital distance at Mars's Equivalent Radiation) : 3.243 AU ( 485198017.0 km)
  • Snow Line (the orbital distance at Snow Line Equivalent Radiation) : 4.773 AU ( 713990137.2 km)
  • Radiation at Planetary Boundary of TOI-257 b : 267117.72 W/m2

    (Habitable zone calculated based on SEAU(Solar Equivalent Astronomical Unit) around the star TOI-257)



  • Kopparapu Recent Venus for Star TOI-257 distance : 1.567 AU
  • Kopparapu Runaway Greenhouse for Earth-sized planet for Star TOI-257 distance : 1.985 AU
  • Kopparapu Runaway Greenhouse for Super-Earth-sized planet for Star TOI-257 distance : 1.917 AU
  • Kopparapu Runaway Greenhouse for Mars-sized planet for Star TOI-257 distance : 2.101 AU
  • Kopparapu Outer Boundary for Maximum Greenhouse for Star TOI-257 distance : 3.480 AU
  • Kopparapu Outer Boundary for Early Mars for Star TOI-257 distance : 3.671 AU

    (Habitable zone calculated based on Kopparapu et al.(2013) around the star TOI-257)



  • Original Kopparapu Recent Venus for Star TOI-257 distance : 1.579 AU
  • Original Kopparapu Runaway Greenhouse for Star TOI-257 distance : 2.038 AU
  • Original Kopparapu Moist Greenhouse for Star TOI-257 distance : 2.090 AU
  • Original Kopparapu Outer Boundary for Maximum Greenhouse for Star TOI-257 distance : 3.542 AU
  • Original Kopparapu Outer Boundary for Early Mars for Star TOI-257 distance : 3.684 AU

    (Habitable zone calculated based on Kopparapu et al.(Original) around the star TOI-257)



    (Position in Stellar Map of star TOI-257 and its Exoplanet TOI-257 b)



    (Zoomed position in Stellar Map of star TOI-257 and its Exoplanet TOI-257 b (zoom level 3))