Astronomy:Gamma Trianguli

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Short description: Star in the constellation Triangulum
γ Trianguli
Location of γ Trianguli (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Triangulum
Right ascension  02h 17m 18.86703s[1]
Declination +33° 50′ 49.8950″[1]
Apparent magnitude (V) +4.01[2]
Characteristics
Spectral type A1Vnn[3]
U−B color index +0.02[2]
B−V color index +0.02[2]
Astrometry
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
Distance112.3 ± 1.0 ly
(34.4 ± 0.3 pc)
Absolute magnitude (MV)+1.35[5]
Details
Mass2.7[6] M☉
Radius2.09±0.04[7] R☉
Luminosity28±1[7] L☉
Temperature9,210±100[7] K
Rotational velocity (v sin i)254[8] km/s
Age300[6] Myr
Other designations
Apdu, γ Tri, 9 Tri, BD+33 397, FK5 79, HD 14055, HIP 10670, HR 664, SAO 55427[9]
Database references
SIMBADdata

Gamma Trianguli, also named Apdu,[10] 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]

Naming

Gamma Trianguli (Latinized from Gamma Tri, abbreviated γ Trianguli, γ Tri) is the star's Bayer designation.

This star was part of the ancient Egyptian constellation Apdu, the Bird, which is identified with the area between Algol and Triangulum. The IAU Working Group on Star Names approved the name Apdu for this star on 13 November 2025 and it is now so entered in the IAU Catalog of Star Names.[10]

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).[12]

Properties

This star has a stellar classification of A1Vnn,[3] which indicates it is an A-type main sequence star. It has 2.7 times the mass of the Sun[6] and 2.09 times Sun's radius.[7] Gamma Trianguli is radiating about 33 times the luminosity of the Sun from its outer envelope[6] at an effective temperature of 9,210 K,[7] giving the star a white hue.[13] The star is roughly 300 million years old.[6]

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.[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.[8] By comparison, the Sun is a slow rotator with an equatorial azimuthal velocity of 2 km/s.[14] 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.[15]

Debris disk

Image of the debris disk with the REASONS survey[7]
Image of the debris disk with the REASONS survey[7]

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.[16]

Gamma Trianguli's circumstellar disk[7]
Disks
(in order from star)
 Radius
(AU) 		Inclination
circumstellar disc 180±10 81.1+0.8
−0.9°

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V  Note: see VizieR catalogue I/311.
  2. ↑ 2.0 2.1 2.2 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. ↑ 3.0 3.1 Cowley, A. et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375–406, doi:10.1086/110819, Bibcode: 1969AJ.....74..375C 
  4. ↑ 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 (Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg) 35: 1, Bibcode: 1999VeARI..35....1W 
  5. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 Wyatt, M. C. et al. (July 2007), "Steady State Evolution of Debris Disks around A Stars", The Astrophysical Journal 663 (1): 365–382, doi:10.1086/518404, Bibcode: 2007ApJ...663..365W 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 Matrà, L.; Marino, S.; Wilner, D. J.; Kennedy, G. M.; Booth, M.; Krivov, A. V.; Williams, J. P.; Hughes, A. M. et al. (2025-01-15). "REsolved ALMA and SMA Observations of Nearby Stars (REASONS): A population of 74 resolved planetesimal belts at millimetre wavelengths". Astronomy and Astrophysics 693. doi:10.1051/0004-6361/202451397. Bibcode: 2025A&A...693A.151M. 
  8. ↑ 8.0 8.1 8.2 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, doi:10.1051/0004-6361:20065224, Bibcode: 2007A&A...463..671R 
  9. ↑ "gam Tri -- Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=gam+Tri, retrieved 2011-12-11 
  10. ↑ 10.0 10.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 
  11. ↑ 11.0 11.1 Kaler, James B., "GAMMA TRI (Gamma Trianguli)", Stars (University of Illinois), http://stars.astro.illinois.edu/sow/gammatri.html, retrieved 2011-12-11 
  12. ↑ Script error: The function "in_lang" does not exist. AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 10 日
  13. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 
  14. ↑ Stix, Michael (2004), The sun: an introduction, Astronomy and astrophysics library (2nd ed.), Springer, p. 423, ISBN 3-540-20741-4, https://books.google.com/books?id=wxHN9jP-mNMC&pg=PA423 
  15. ↑ 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, https://books.google.com/books?id=ZEKO2pzuRHoC&pg=PA88 
  16. ↑ 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, doi:10.1086/509912, Bibcode: 2007ApJ...660.1556R 



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