Gamma Trianguli

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γ Trianguli
Diagram showing star positions and boundaries of the Triangulum constellation and its surroundings
Cercle rouge 100%.svg

Location of γ Trianguli (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum
Right ascension 02h 17m 18.86703s[1]
Declination +33° 50′ 49.8950″[1]
Apparent magnitude (V) +4.01[2]
Spectral type A1Vnn[3]
U−B color index +0.02[2]
B−V color index +0.02[2]
Radial velocity (Rv) +9.9[4] km/s
Proper motion (μ) RA: 44.64[1] mas/yr
Dec.: –52.57[1] mas/yr
Parallax (π) 29.04 ± 0.25[1] mas
Distance 112.3 ± 1.0 ly
(34.4 ± 0.3 pc)
Mass 2.7[5] M
Radius 1.96[6] R
Luminosity 33.0[5] L
Temperature 9,440[7] K
Rotational velocity (v sin i) 254[8] km/s
Age 3.0 × 108[5] years
Other designations
γ Trianguli, γ Tri, Gamma Tri, 9 Trianguli, BD+33 397, FK5 79, HD 14055, HIP 10670, HR 664, SAO 55427.[9]

Gamma Trianguli (Gamma Tri, γ Trianguli, γ Tri) is a star in the constellation Triangulum located approximately 112 light years from Earth. It has an apparent magnitude of +4.03 and forms an optical (line-of-sight) triple with Delta Trianguli and 7 Trianguli.[10]

This star has a stellar classification of A1Vnn,[3] which indicates it is an A-type main sequence star. It has 2.7[5] times the mass of the Sun and nearly double the Sun's radius.[6] Gamma Trianguli is radiating about 33[5] times the luminosity of the Sun from its outer envelope at an effective temperature of 9,440 K,[7] giving the star a white hue.[11] The star is roughly 300 million years old.[5]

It is rotating rapidly, with a projected rotational velocity of 254 km/s along the equator,[8] which causes the star to take the pronounced shape of an oblate spheroid like Altair.[10] Because the inclination of the star's axial tilt is unknown, this means that the azimuthal equatorial velocity is at least this amount and possibly higher.[8] By comparison, the Sun is a slow rotator with an equatorial azimuthal velocity of 2 km/s.[12] The doppler shift from the rapid rotation results in very diffuse absorption lines in the star's spectrum, as indicated by the 'nn' in the classification.[13]

Orbiting the star is a dusty debris disk with a combined mass of about 2.9 × 10−2 times the mass of the Earth. This disk can be detected because it is being heated to a temperature of about 75 K by Gamma Trianguli and is radiating this as infrared energy. The disk is separated from the host star by an angle of 2.24 arcseconds, corresponding to a physical radius of 80 AU, or 80 times the separation of the Earth from the Sun.[6]


In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of γ Trianguli, γ Andromedae, φ Persei, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, and δ Trianguli. Consequently, γ Trianguli itself is known as 天大將軍十 (Tiān Dà Jiāng Jūn shí, English: the Tenth Star of Heaven's Great General.).[14]

See also[edit]


  1. ^ a b c d e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357  Note: see VizieR catalogue I/311.
  2. ^ a b c Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819 
  4. ^ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, 35, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W 
  5. ^ a b c d e f Wyatt, M. C.; et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal, 663 (1): 365–382, arXiv:astro-ph/0703608Freely accessible, Bibcode:2007ApJ...663..365W, doi:10.1086/518404 
  6. ^ a b c Rhee, Joseph H.; Song, Inseok; Zuckerman, B.; McElwain, Michael (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555Freely accessible, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912 
  7. ^ a b Zorec, J.; et al. (July 2009), "Fundamental parameters of B supergiants from the BCD system. I. Calibration of the (λ_1, D) parameters into Teff", Astronomy and Astrophysics, 501 (1): 297–320, arXiv:0903.5134Freely accessible, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147 
  8. ^ a b c 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/0610785Freely accessible, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224 
  9. ^ "gam Tri -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-11 
  10. ^ a b Kaler, James B., "GAMMA TRI (Gamma Trianguli)", Stars, University of Illinois, retrieved 2011-12-11 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16 
  12. ^ Stix, Michael (2004), The sun: an introduction, Astronomy and astrophysics library (2nd ed.), Springer, p. 423, ISBN 3-540-20741-4 
  13. ^ Kaler, James B. (2011), Stars and Their Spectra: An Introduction to the Spectral Sequence (2nd ed.), Cambridge University Press, p. 88, ISBN 0-521-89954-0 
  14. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日