Epsilon Trianguli

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

Location of ε Trianguli (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Triangulum
Right ascension 02h 02m 57.95579s[1]
Declination +33° 17′ 02.8813″[1]
Apparent magnitude (V) +5.50[2]
Spectral type A2 V[3]
U−B color index +0.06[2]
B−V color index +0.03[2]
Radial velocity (Rv) 3.3[4] km/s
Proper motion (μ) RA: –15.97[1] mas/yr
Dec.: –7.22[1] mas/yr
Parallax (π) 8.33 ± 0.34[1] mas
Distance 390 ± 20 ly
(120 ± 5 pc)
Radius 3.28[5] R
Surface gravity (log g) 3.76[6] cgs
Temperature 10,000[5] K
Rotational velocity (v sin i) 107[7] km/s
Age 600[5] Myr
Other designations
ε Trianguli, ε Tri, Epsilon Tri, 3 Trianguli, BD+32 369, HD 12471, HIP 9570, HR 599, SAO 55218.[8]

Epsilon Trianguli (Epsilon Tri, ε Trianguli, ε Tri) is a binary star in the constellation Triangulum. Based upon measurement of its trigonometric parallax, it is approximately 390 light years from Earth.[1]

The primary component is an A-type main sequence star with a stellar classification of A2 V,[3] an apparent magnitude of +5.50 and an estimated age of 600 million years.[5] The radius of this star is more than three times the radius of the Sun, and the photosphere has an effective temperature of about 10,000.[5] The secondary component has an apparent magnitude of 11.4 and is separated from the primary by an angle of 3.9 arcseconds.[9]

An excess emission of infrared radiation suggests the presence of a dusty disk in orbit about the primary. This disk has a mean radius of 105 AU, or 105 times the separation of the Earth from the Sun, and is radiating at a temperature of 85 K.[5]

This star system is a probable member of the Ursa Major Moving Group of stars that share a common motion through space.[6] The space velocity components of Epsilon Trianguli are [U, V, W] = [+11.8, +11.4, –3.8] km/s.[10]


  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:0708.1752free to read. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  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. ^ Wilson, Ralph Elmer (1953), General catalogue of stellar radial velocities, Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W 
  5. ^ a b c d e f Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555free to read, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912 
  6. ^ a b Monier, R. (November 2005), "Abundances of a sample of A and F-type dwarf members of the Ursa Major Group", Astronomy and Astrophysics, 442 (2): 563–566, Bibcode:2005A&A...442..563M, doi:10.1051/0004-6361:20053222 
  7. ^ 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/0610785free to read, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224 
  8. ^ "eps Tri -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-13 
  9. ^ 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:0806.2878free to read, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x 
  10. ^ King, Jeremy R.; et al. (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