π3 Orionis
Red circle.svg
Location of π3 Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Orion
Right ascension 04h 49m 50.41091s[1]
Declination +06° 57′ 40.5883″[1]
Apparent magnitude (V) 3.16[2]
Spectral type F6 V[2]
U−B color index +0.00[2]
B−V color index +0.46[2]
Variable type Suspected[3]
Radial velocity (Rv)24.1[4] km/s
Proper motion (μ) RA: 464.06[1] mas/yr
Dec.: 11.21[1] mas/yr
Parallax (π)123.94 ± 0.17[1] mas
Distance26.32 ± 0.04 ly
(8.07 ± 0.01 pc)
Absolute magnitude (MV)3.65[5]
Mass1.236[6] M
Radius1.323 ± 0.004[7] R
Luminosity2.822 ± 0.030[7] L
Surface gravity (log g)4.4[8] cgs
Temperature6,516 ± 19[7] K
Metallicity [Fe/H]0.02[8] dex
Rotational velocity (v sin i)17[9] km/s
Age1.4[5] Gyr
Other designations
Tabit, π3 Ori, 1 Ori, BD+06°762, FK5 1134, GCTP 1077.00, Gliese 178, HD 30652, HIP 22449, HR 1543, LTT 11517, SAO 112106[10]
Database references

Pi3 Orionis (π3 Orionis, abbreviated Pi3 Ori, π3 Ori), also named Tabit /ˈtbɪt/,[11][12] is a star in the equatorial constellation of Orion. At an apparent visual magnitude of 3.16,[2] it is readily visible to the naked eye and is the brightest star in the lion's hide (or shield) that Orion is holding. As measured using the parallax technique, it is 26.32 light-years (8.07 parsecs) distant from the Sun.[1]


π3 Orionis (Latinised to Pi3 Orionis) is the system's Bayer designation.

It bore the traditional name of 'Tabit', from the Arabic الثابت al-thābit 'the endurer (the fixed/constant one)'.[13] In 2016, the IAU organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN approved the name Tabit for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[12]

In Chinese, 參旗 (Sān Qí), meaning Banner of Three Stars, refers to an asterism consisting of π3 Orionis, ο1 Orionis, ο2 Orionis, 6 Orionis, π1 Orionis, π2 Orionis, π4 Orionis, π5 Orionis and π6 Orionis.[15] Consequently, the Chinese name for Pi3 Orionis itself is 參旗六 (Zhāng Qí Liù), "the Sixth Star of Banner of Three Stars".[16]

According to Richard Hinckley Allen: Star Names – Their Lore and Meaning, this star, together with ο1 Orionis, ο2 Orionis, π1 Orionis, π2 Orionis, π4 Orionis, π5 Orionis, π6 Orionis and 6 Orionis (are all of the 4th to the 5th magnitudes and in a vertical line), indicate the lion's skinwere but Al Tizini said that they were the Persians' Al Tāj, "the Crown", or "Tiara", of their kings; and the Arabians' Al Kumm, "the Sleeve", of the garment in which they dressed the Giant, the skin being omitted. Ulugh Beg called them Al Dhawāib, "Anything Pendent"; and the Borgian globe had the same, perhaps originated it. Al Sufi's title was Manica, a Latin term for a protecting Gauntlet; and Grotius gave a lengthy dissertation on the Mantile, which some anonymous person applied to them, figured as a cloth thrown over the Giant's arm.[17]


Pi3 Orionis is most likely single; a nearby star is probably an optical companion.[18]

It is a main-sequence star of spectral type F6 V. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[19] Compared to the Sun, it has about 124%[6] of the mass, 132% of the radius, and nearly 3 times the luminosity.[7] This energy is being radiated from the star's outer atmosphere at an effective temperature of 6,516 K,[7] giving it the yellow-white glow of an F-type star.

Although a periodicity of 73.26 days has been observed in the star's radial velocity, it seems likely to be bound more to stellar activity than to a planetary object in close orbit. No substellar companion has been detected so far around Pi3 Orionis and the McDonald Observatory team has set limits to the presence of one or more planets[20] with masses between 0.84 and 46.7 Jupiter masses and average separations spanning between 0.05 and 5.2 astronomical units. Thus, so far it appears that planets could easily orbit in the habitable zone without any complications caused by a gravitationally perturbing body.

See also


  1. ^ a b c d e f van Leeuwen, F. (November 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.
  2. ^ a b c d e Johnson, H. L.; Morgan, W. W. (1953), "Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas", Astrophysical Journal, 117: 313–352, Bibcode:1953ApJ...117..313J, doi:10.1086/145697.
  3. ^ Kukarkin, B. V.; et al. (1981), "Nachrichtenblatt der Vereinigung der Sternfreunde e.V. (Catalogue of suspected variable stars)", Nachrichtenblatt der Vereinigung der Sternfreunde, Moscow: Academy of Sciences USSR Shternberg, Bibcode:1981NVS...C......0K.
  4. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E.
  5. ^ a b Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics Supplement Series, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511. Note: see VizieR catalogue V/130.
  6. ^ a b Takeda, G.; et al. (2007), "Stellar parameters of nearby cool stars. II. Physical properties of ~1000 cool stars from the SPOCS catalog", Astrophysical Journal Supplement Series, 168 (2): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763, S2CID 18775378 Note: see VizieR catalogue J/ApJS/168/297.
  7. ^ a b c d e 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. ^ a b Kuroczkin, D.; Wiszniewski, A. (1997), "The problem of iron abundance in the SMR stars.", Acta Astronomica, 27: 145–150, Bibcode:1977AcA....27..145K.
  9. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
  10. ^ "pi03 Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-01-07.
  11. ^ Rumrill, H. B. (June 1936). "Star Name Pronunciation". Publications of the Astronomical Society of the Pacific. San Francisco, California. 48 (283): 139. Bibcode:1936PASP...48..139R. doi:10.1086/124681.
  12. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  13. ^ Moore, Patrick; Rees, Robin (2011), Patrick Moore's Data Book of Astronomy (2nd ed.), Cambridge University Press, p. 460, ISBN 978-0521899352
  14. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  15. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. ^ Allen, R. H. (1963) [1899], "Orion", Star Names: Their Lore and Meaning (Dover ed.), New York, NY: Dover Publications Inc, p. 320, ISBN 0-486-21079-0, retrieved 2018-07-28.
  18. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  19. ^ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
  20. ^ Wittenmyer, Robert A.; et al. (July 2006), "Detection Limits from the McDonald Observatory Planet Search Program", The Astronomical Journal, 132 (1): 177–188, arXiv:astro-ph/0604171, Bibcode:2006AJ....132..177W, doi:10.1086/504942, S2CID 16755455.