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γ Trianguli
	Location of γ Trianguli (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Triangulum
Right ascension	02h 17m 18.86703s
Declination	+33° 50′ 49.8950″
Apparent magnitude (V)	+4.01
Characteristics
Spectral type	A1Vnn
U−B color index	+0.02
B−V color index	+0.02
Astrometry
Radial velocity (Rv)	+9.9 km/s
Proper motion (μ)	RA: 44.64 mas/yr ; Dec.: –52.57 mas/yr
Parallax (π)	29.04 ± 0.25 mas
Distance	112.3 ± 1.0 ly ; (34.4 ± 0.3 pc)
Absolute magnitude (MV)	+1.35
Details
Mass	2.7 M☉
Radius	1.96 R☉
Luminosity	33.0 L☉
Temperature	9,440 K
Rotational velocity (v sin i)	254 km/s
Age	300 Myr
Other designations
	γ Trianguli, γ Tri, Gamma Tri, 9 Trianguli, BD+33 397, FK5 79, HD 14055, HIP 10670, HR 664, SAO 55427
Database references
SIMBAD	data

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 +4.01 and forms an optical (line-of-sight) triple with Delta Trianguli and 7 Trianguli.^[11]

Properties

This star has a stellar classification of A1Vnn,^[3] which indicates it is an A-type main sequence star. It has 2.7^[6] times the mass of the Sun and nearly double the Sun's radius.^[7] Gamma Trianguli is radiating about 33^[6] times the luminosity of the Sun from its outer envelope at an effective temperature of 9,440 K,^[8] giving the star a white hue.^[12] The star is roughly 300 million years old.^[6]

Rotation

It is rotating rapidly, with a projected rotational velocity of 254 km/s along the equator,^[9] which causes the star to take the pronounced shape of an oblate spheroid like Altair.^[11] 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.^[9] By comparison, the Sun is a slow rotator with an equatorial azimuthal velocity of 2 km/s.^[13] 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.^[14]

Debris disk

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.^[7]

Naming

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, the Chinese name for γ Trianguli itself is 天大將軍十 (Tiān Dà Jiāng Jūn shí, English: the Tenth Star of Heaven's Great General.).^[15]

References

^ ^a ^b ^c ^d ^e van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600 Note: see VizieR catalogue I/311.
^ ^a ^b ^c 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
^ ^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
^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
^ 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, S2CID 119257644.
^ ^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/0703608, Bibcode:2007ApJ...663..365W, doi:10.1086/518404, S2CID 18883195
^ ^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/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505
^ ^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:0903.5134, Bibcode:2009A&A...501..297Z, doi:10.1051/0004-6361/200811147, S2CID 14969137
^ ^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/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298
^ "gam Tri -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-11
^ ^a ^b Kaler, James B., "GAMMA TRI (Gamma Trianguli)", Stars, University of Illinois, retrieved 2011-12-11
^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
^ Stix, Michael (2004), The sun: an introduction, Astronomy and astrophysics library (2nd ed.), Springer, p. 423, ISBN 3-540-20741-4
^ Kaler, James B. (2011), Stars and Their Spectra: An Introduction to the Spectral Sequence (2nd ed.), Cambridge University Press, p. 88, ISBN 978-0-521-89954-3
^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日 Archived 2011-07-16 at the Wayback Machine