Article · Wikipedia archive · Last revised Jul 19, 2026

7 Trianguli

7 Trianguli is a solitary star located in the northern constellation Triangulum. It has an apparent magnitude of 5.25, making it faintly visible to the naked eye under ideal conditions. The star is situated at distance of 360 light years but is approaching with a heliocentric radial velocity of −1.3 km/s, which is poorly constrained.

Last revised
Jul 19, 2026
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≈ 3 min
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7 Trianguli
Location of 7 Trianguli (circled)
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Triangulum
Right ascension 02h 15m 56.2876s1
Declination +33° 21′ 32.032″1
Apparent magnitude (V) 5.25±0.012
Characteristics
Evolutionary stage main sequence1
Spectral type A0 V3 or B9.5 V4
U−B color index −0.035
B−V color index −0.015
Astrometry
Radial velocity (Rv)−1.3±26 km/s
Proper motion (μ) RA: −15.2341 mas/yr
Dec.: −32.7111 mas/yr
Parallax (π)9.0683±0.137 mas1
Distance360 ± 5 ly
(110 ± 2 pc)
Absolute magnitude (MV)0.587
Details
Mass2.778 M☉
Radius3.24±0.119 R☉
Luminosity89.1+10.5
−8.19 L☉
Surface gravity (log g)4.02±0.148 cgs
Temperature10685±3638 K
Rotational velocity (v sin i)13010 km/s
Age2838 Myr
Other designations
7 Trianguli, AG+33°210, BD+32°409, GC 2710, HD 13869, HIP 10559, HR 655, SAO 55397
Database references
SIMBADdata

7 Trianguli is a solitary11 star located in the northern constellation Triangulum. It has an apparent magnitude of 5.25,2 making it faintly visible to the naked eye under ideal conditions. The star is situated at distance of 360 light years1 but is approaching with a heliocentric radial velocity of −1.3 km/s,6 which is poorly constrained.

7 Trianguli has a stellar classification of A0 V3 or B9.5 V,4 depending on the study. At present it has 2.77 times the mass of the Sun8 and 3.24 times the radius of the Sun.9 It shines at 89.1 times the luminosity of the Sun9 from its photosphere at an effective temperature of 10,685 K,8 giving it a blueish white glow. 7 Trianguli is a young star, with an age of 283 million years8 and spins rapidly with a projected rotational velocity of 130 km/s.10 It has been classified as having a peculiar spectrum,12 but it is considered doubtful that it is actually a chemically peculiar star.13

It was once designated Eta Trianguli by John Flamsteed and was included in his Atlas Coelestis, but the designation is now dropped.14

Together with δ Trianguli and γ Trianguli, it forms an optical (line-of-sight) triple.

References

References

  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. Cowley, A.; Cowley, C.; Jaschek, M.; Jaschek, C. (April 1969). "A study of the bright stars. I. A catalogue of spectral classifications". The Astronomical Journal. 74: 375. Bibcode:1969AJ.....74..375C. doi:10.1086/110819. ISSN 0004-6256.
  4. Eggen, O. J. (1962). "Space-velocity vectors for 3483 stars with proper motion and radial velocity". Royal Greenwich Observatory Bulletins. 51: 79. Bibcode:1962RGOB...51...79E.
  5. Hamdy, M. A.; Abo Elazm, M. S.; Saad, S. M. (1993). "A catalogue of spectral classification and photometric data of B-type stars". Astrophysics and Space Science. 203 (1): 53–107. Bibcode:1993Ap&SS.203...53H. doi:10.1007/BF00659414. ISSN 0004-640X.
  6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication: 0. Bibcode:1953GCRV..C......0W.
  7. 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.
  8. David, Trevor J.; Hillenbrand, Lynne A. (12 May 2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. ISSN 0004-637X.
  9. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
  10. Glebocki, R.; Gnacinski, P.; Stawikowski, A. (December 2000). "Catalog of Projected Rotational Velocities". Acta Astronomica. 50: 509–515. Bibcode:2000AcA....50..509G. ISSN 0001-5237.
  11. 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
  12. Cucchiaro, A.; Jaschek, M.; Jaschek, C.; Macau-Hercot, D. (1980). "Spectral classification from the ultraviolet line features of S2/68 spectra". Astronomy and Astrophysics Supplement Series. 40: 207. Bibcode:1980A&AS...40..207C.
  13. Renson, P.; Manfroid, J. (May 2009). "Catalogue of Ap, HgMn and Am stars". Astronomy and Astrophysics. 498 (3): 961–966. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788.
  14. Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 209–223, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625.