Chi1 Orionis A
Chi 1 orionis diagram vectorized.svg

Star map of the Bayers Stars in Orion. Chi1 Orionis is indicated.
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 54m 22.98s[1]
Declination +20° 16′ 34.2″[1]
Apparent magnitude (V) 4.38 - 4.41[2]
Spectral type G0 V[3]
U−B color index 0.07
B−V color index 0.59
Variable type RS CVn[2]
Radial velocity (Rv)−13.4 km/s
Proper motion (μ) RA: −162.54±0.28[1] mas/yr
Dec.: −99.51±0.16[1] mas/yr
Parallax (π)115.43 ± 0.27 mas[1]
Distance28.26 ± 0.07 ly
(8.66 ± 0.02 pc)
Absolute magnitude (MV)4.82±0.005[4]
Period (P)5156.291±2.508 d
Semi-major axis (a)89.662±0.880 Mas
Eccentricity (e)0.452±0.002
Inclination (i)95.937±0.790°
Longitude of the node (Ω)126.360±0.593°
Periastron epoch (T)2451468.2±3.083 JD
Argument of periastron (ω)
Semi-amplitude (K1)
1.876±0.003 km/s
Mass1.01[6] M
Radius0.979 ± 0.009[7] R
Luminosity1.081 ± 0.018[7] L
Surface gravity (log g)4.39[6] cgs
Temperature5,955 ± 6.1[8] K
Metallicity [Fe/H]−0.01[9] dex
Rotation5.2 days[9]
Rotational velocity (v sin i)8.7[6] km/s
Age300–400[10] Myr
Mass0.15[6] M
Age70-130[6] Myr
Other designations
54 Ori, Gl 222, HR 2047, BD+20°1162, HD 39587, LTT 11743, GCTP 1354.00, SAO 77705, HIP 27913.
Database references

Chi1 Orionis1 Ori, χ1 Orionis) is a star about 28 light years away.[1] It is in the constellation Orion, where it can be seen in the tip of the Hunter's upraised club.[11]

χ1 Ori is a G0V star.[6] It has a faint companion with a mass estimated at about 15% of the mass of the Sun, and an orbital period of 14.1 years. The companion orbits an average distance of 6.1 AU from the primary, but has a fairly high orbital eccentricity, ranging from 3.3 AU out to 8.9 AU from the primary. Because of this red dwarf companion, the likelihood of habitable planets in this system is low. It is thought that the companion is a red dwarf still contracting towards the main sequence.[6]

A necessary condition for the existence of a planet in this system are stable zones where the object can remain in orbit for long intervals. For hypothetical planets in a circular orbit around the individual members of this star system, this maximum orbital radius is computed to be 1.01 AU for the primary and 0.41 AU for the secondary. (Note that the orbit of the Earth is 1 AU from the Sun.) A planet orbiting outside of both stars would need to be at least 18.4 AU distant.[12]

χ1 Ori is a candidate stream star member of the Ursa Major Moving Group, although there is some evidence to the contrary.[9]

See also


  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. ^ a b Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  3. ^ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. ^ Park, Sunkyung; et al. (2013). "Wilson-Bappu Effect: Extended to Surface Gravity". The Astronomical Journal. 146 (4): 73. arXiv:1307.0592. Bibcode:2013AJ....146...73P. doi:10.1088/0004-6256/146/4/73. S2CID 119187733.
  5. ^ Han, Inwoo; Gatewood, George (2002). "A Precise Orbit Determination of χ1Orionis from Astrometric and Radial Velocity Data". Publications of the Astronomical Society of the Pacific. 114 (792): 224–228. Bibcode:2002PASP..114..224H. doi:10.1086/338367.
  6. ^ a b c d e f g König, B.; Fuhrmann, K.; Neuhäuser, R.; Charbonneau, D.; Jayawardhana, R. (2002). "Direct detection of the companion of chi 1 Orionis". Astronomy and Astrophysics. 394. arXiv:astro-ph/0209404. Bibcode:2002A&A...394L..43K. doi:10.1051/0004-6361:20021377. S2CID 10411048.
  7. ^ a b Boyajian, Tabetha S.; et al. (February 2012). "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars". The Astrophysical Journal. 746 (1): 101. arXiv:1112.3316. Bibcode:2012ApJ...746..101B. doi:10.1088/0004-637X/746/1/101. S2CID 18993744.. See Table 10.
  8. ^ Kovtyukh; et al. (2003). "High precision effective temperatures for 181 F-K dwarfs from line-depth ratios". Astronomy and Astrophysics. 411 (3): 559–564. arXiv:astro-ph/0308429. Bibcode:2003A&A...411..559K. doi:10.1051/0004-6361:20031378. S2CID 18478960.
  9. ^ a b c Maldonado, J.; et al. (October 2010). "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups". Astronomy and Astrophysics. 521: A12. arXiv:1007.1132. Bibcode:2010A&A...521A..12M. doi:10.1051/0004-6361/201014948. S2CID 119209183.
  10. ^ Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785. S2CID 27151456.
  11. ^ Jim Kaler, Chi-1 Orionis.
  12. ^ Jaime, Luisa G.; et al. (December 2012). "Regions of dynamical stability for discs and planets in binary stars of the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 427 (4): 2723–2733. arXiv:1208.2051. Bibcode:2012MNRAS.427.2723J. doi:10.1111/j.1365-2966.2012.21839.x. S2CID 118570249.