Gamma Ceti

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Gamma Ceti
Diagram showing star positions and boundaries of the Cetus constellation and its surroundings
Cercle rouge 100%.svg
Location of γ Ceti (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension  02h 43m 18.03910s[1]
Declination +03° 14′ 08.9390″[1]
Apparent magnitude (V) 3.47[2] (3.56/6.63/10.16)[3]
Spectral type A3 V + F3 V + K5[3]
U−B color index +0.07[2]
B−V color index +0.09[2]
Radial velocity (Rv)–5.1[4] km/s
Proper motion (μ) RA: –146.10[1] mas/yr
Dec.: –146.12[1] mas/yr
Parallax (π)40.97 ± 0.63[1] mas
Distance80 ± 1 ly
(24.4 ± 0.4 pc)
Absolute magnitude (MV)+1.53[5]
γ Cet A
Mass1.88[6] M
Radius1.9[7] R
Luminosity21[5] L
Surface gravity (log g)4.3[8] cgs
Temperature8,551[8] K
Metallicity [Fe/H]0.00[9] dex
Rotational velocity (v sin i)186[10] km/s
Age647[8] Myr
γ Cet B
Mass1.17[6] M
Temperature6,051[8] K
Rotational velocity (v sin i)10[8] km/s
Other designations
γ Cet, 86 Ceti, BD+02 422, HD 16970, HIP 12706, HR 804, SAO 110707, WDS 02433+0314[11]
Database references

Gamma Ceti (γ Ceti, abbreviated Gamma Cet, γ Cet) is a triple star system in the equatorial constellation of Cetus. It has a combined apparent visual magnitude of 3.47.[2] Based upon parallax measurements, this star is located at a distance of about 80 light-years (24.4 parsecs) from the Sun.[1]

The three components are designated Gamma Ceti A (officially named Kaffaljidhma /ˌkæfəlˈɪdmə/, the traditional name for the entire system),[12] B and C.


γ Ceti (Latinised to Gamma Ceti) is the system's Bayer designation. The designations of the three components as Gamma Ceti A, B and C derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU);[13] the close pair AB is also designated HIP 12706 and HD 16970, and HR 804. The system of A, B, and C is collectively designated GJ 106.1 in the Gliese Catalogue of Nearby Stars.

Gamma Ceti bore the traditional names of Al Kaff al Jidhmah, or Kaffaljidhma, derived from the Arabic الكف الجذماء al-kaf al-jaðmāʼ "the cut-short hand."[14] According to a 1971 NASA memorandum, Al Kaff al Jidhmah was originally the title for five stars: Gamma Ceti as Kafaljidma, Xi¹ Cet as Al Kaff al Jidhmah I, Xi² Ceti as Al Kaff al Jidhmah II, Delta Ceti as Al Kaff al Jidhmah III and Mu Ceti as Al Kaff al Jidhmah IV (excluding Alpha Ceti and Lambda Ceti);[15] the IAU Working Group on Star Names (WGSN)[16] approved the name Kaffaljidhma for the component Gamma Ceti A on February 1, 2017.[12]

In Chinese, 天囷 (Tiān Qūn), meaning Circular Celestial Granary, refers to an asterism consisting of Gamma Ceti, Alpha Ceti, Kappa¹ Ceti, Lambda Ceti, Mu Ceti, Xi¹ Ceti, Xi² Ceti, Nu Ceti, Delta Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for Gamma Ceti itself is 天囷八 (Tiān Qūn bā, English: the Eighth Star of Circular Celestial Granary).[17]

Triple system[edit]

Gamma Ceti appears to be a triple star system;[18] the inner pair (A and B) have an angular separation of 2.6 arcseconds. The primary component of this pair (A) is a visual magnitude 3.6, A-type main sequence star with a stellar classification of A3 V. The fainter secondary component (B) is an F-type main sequence star that has a classification of F3 V and a magnitude of 6.6.[3] The contrasting colors of these two stars makes them a popular target of amateur astronomers; the two can be resolved with a small, 4 in (10 cm) aperture telescope under ideal seeing conditions, although at times they can be a challenge to resolve even with a much larger scope.[19]

At a wide separation of 840 arcseconds is component C, a dim, magnitude 10.2 K-type star with the designation BD+02 418.[3] It shares a common proper motion with A and is at a very similar distance,[20][18] but is separated from the close pair by over 20,000 au.[21] It has a spectral classification of K5V.[22] There are several other stars brighter and closer to Gamma Ceti than BD+02 418 - BD+02 419, HD 16985, and TYC 50-1274-1 - but they are all more distant background stars.


The measured angular diameter of the primary star is 0.74 ± 0.08 mas.[23] At the estimated distance of this system, this yields a physical size of about 1.9 times the radius of the Sun.[7] The secondary component of this system is an X-ray source with a luminosity of 2.2 × 1029 erg s−1.[24] Gamma Ceti is about 300[25] million years old and it appears to be a member of the stream of stars loosely associated with the Ursa Major moving group;[26] the primary has been examined for an excess of infrared emission that would suggest the presence of circumstellar matter, but none was found.[25]


  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
  2. ^ a b c d Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. ^ a b c d 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
  4. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.c. Publication: 0, Bibcode:1953GCRV..C......0W
  5. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. ^ a b Tokovinin, A.; Kiyaeva, O. (2016). "Eccentricity distribution of wide binaries". Monthly Notices of the Royal Astronomical Society. 456 (2): 2070. Bibcode:2016MNRAS.456.2070T.
  7. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 978-3-540-29692-8. The radius (R*) is given by:
  8. ^ a b c d e Gullikson, Kevin; Kraus, Adam; Dodson-Robinson, Sarah (2016). "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars". The Astronomical Journal. 152 (2): 40. arXiv:1604.06456. Bibcode:2016AJ....152...40G.
  9. ^ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. Bibcode:2003AJ....126.2048G.
  10. ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224
  11. ^ "gam Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-04.
  12. ^ a b "Naming Stars". Retrieved 16 December 2017.
  13. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  14. ^ Allen, Richard Hinckley (1963), Star Names: Their Lore and Meaning (Dover ed.), University of Chicago, p. 160
  15. ^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology
  16. ^ "International Astronomical Union | IAU". Retrieved 2017-04-01.
  17. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
  18. ^ a b "Washington Double Star Catalog". United States Naval Observatory. Retrieved 2 January 2018.
  19. ^ Mollise, Rod (2006), The urban astronomer's guide: a walking tour of the cosmos for city sky watchers, Patrick Moore's practical astronomy series, Springer, p. 200, ISBN 978-1-84628-216-4
  20. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  21. ^ Dhital, Saurav; West, Andrew A.; Stassun, Keivan G.; Bochanski, John J. (2010). "Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES): A Catalog of Very Wide, Low-mass Pairs". The Astronomical Journal. 139 (6): 2566. Bibcode:2010AJ....139.2566D.
  22. ^ Stephenson, C. B. (1986). "Dwarf K and M stars of high proper motion found in a hemispheric survey". The Astronomical Journal. 92: 139. Bibcode:1986AJ.....92..139S.
  23. ^ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
  24. ^ Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429
  25. ^ a b Su, K. Y. L.; et al. (December 2006), "Debris Disk Evolution around A Stars", The Astrophysical Journal, 653 (1): 675–689, arXiv:astro-ph/0608563, Bibcode:2006ApJ...653..675S, doi:10.1086/508649
  26. ^ King, Jeremy R.; Villarreal, Adam R.; Soderblom, David R.; Gulliver, Austin F.; Adelman, Saul J. (April 2003), "Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group", The Astronomical Journal, 125 (4): 1980–2017, Bibcode:2003AJ....125.1980K, doi:10.1086/368241

External links[edit]