Delta Trianguli 2
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The Delta Trianguli system is located about 35.4 light-years from Sol. It lies in the north central part (2:17:3.2:+34:13:27.2, ICRS 2000.0) of Constellation Triangulum, the Triangle -- near Gamma and 7 Trianguli, slightly southeast of Beta Trianguli and northeast of Mothallah (Alpha Trianguli) and Hamal (Alpha Arietis). According to the Yale Bright Star Catalogue, 1991 5th Revised Edition notes entry for HR 660, the system is a member of the Zeta Herculis stellar moving group. (See an animation of the stellar and potentially habitable zone orbits of the Delta Trianguli AB system, with a table of basic orbital and physical characteristics.)
Delta Trianguli A is a yellow-orange main sequence dwarf star of spectral and luminosity type G0.5 Ve. It may have as much as 109 percent of Sol's mass, 98 percent of its diameter (Johnson and Wright, 1983, page 649), and as much as 1.1 times its visual luminosity. The star may be only 13 to 31 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 279). It is known to have a double-lined, spectroscopic stellar companion "B" of lower mass. Useful catalogue numbers and designations for the star include: 8 Tri A, Del Tri A, HR 660*, Gl 92 A, Hip 10644, HD 13974, BD+33 395, SAO 55420, LHS 154, LTT 10770, LFT 198, and ADS 1739 A.
According to the new Sixth Catalog of Visual Orbits of Binary Stars, Stars A and B are separated on average by less than 0.11 AU (a= 0.0098" at a HIPPARCOS distance estimate of 35.4 ly). Their highly circular orbit (e= 0.020) takes only about 10.02 days (0.02743 years) to complete and is inclined around 167° from Earth's perspective (Hummel et al, 1995, pp. 389 to 390). According to calculations available from the Flagstaff Station of the U.S. Naval Observatory, orbit elements derived from possibly more recent MARK III observational data are slightly different: a = 0.00993"; e=0.012; i= 157 +/- 2 degrees; and P= 10.02 days. (See also "Delta Tri" in the Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Systems.)
© Torben Krogh & Mogens Winther,
(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)
Star B may be an orange-red
dwarf star, somewhat similar to
Epsilon Eridani at left center of
According to Hummel et al (1995, page 390), the companion object may be a star as orange in color as a spectral and luminosity type of K4 V, but error margins in their calculations "prevent any meaningful physical discussion of Delta Trianguli until better interferometric measurements are available." Useful catalogue numbers and designations for the star include: Del Tri B, Gl 92 B, and ADS 1739 B.
The orbit of an Earth-like planet (with liquid water) around close-orbiting Stars A and B may be centered as close as 1.06 AU -- between the orbital distances of Earth and Mars in the Solar System -- with an orbital period of over 384 days (1.05 years). Astronomers would find it very difficult to detect an Earth-type planet in the water zone of this star using present methods. (See an animation of the stellar and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)
The following table includes all star systems known to be located within 10 light-years (ly), plus more bright stars within 10 to 20 ly, of Delta Trianguli.
|Star System||Spectra &|
|LP 245-10||M V||1.8|
|L 1305-10||M4-6 V||6.9|
|HR 483 AB||G1.5 V |
|BD+47 612||M1.5 Ve||9.5|
|Theta Persei 2?||F7 V |
|* plus bright stars *||. . .|
|Iota Persei||G0 V||11|
|Upsilon Andromedae||F7-8 V||11|
|Mu Cassiopeiae AB||G5 VIp |
|BD+37 783||G5 V||18|
|Kappa Ceti||G5 Ve||20|
Try Professor Jim Kaler's Stars site for other information about Delta Trianguli at the University of Illinois' Department of Astronomy. In addition, the late John Whatmough created illustrated web pages on this system at Extrasolar Visions.
Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS (Star A and Star B), and the Nearby Stars Database. Additional information may be available at Roger Wilcox's Internet Stellar Database and www.alcyone.de's entry for HR 660.
According to the Ancient Greeks, Constellation Triangulum may represent the island Sicily, having been honored by Zeus (the chief of the Greek Gods) with an eternal position among the stars. For more information about the stars and objects in this constellation, go to Christine Kronberg's Triangulum. For an illustration, see David Haworth's Triangulum.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
Note: Nominated as a "notable nearby star" by Erik Allan Edler.
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