Alpha Trianguli
{{short description|Star in the constellation Triangulum}}
{{Starbox begin
| name = α Trianguli
}}
{{Starbox image
| image=
{{Location mark
|image=Triangulum constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=12|mark_link=α Trianguli
|x=662|y=530
}}
|caption=Location of α Trianguli (circled)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Triangulum
| dec = {{DEC|+29|34|43.7801}}
}}
{{Starbox character
| class = F5III to F6IV + M
| variable = Ellipsoidal
}}
{{Starbox astrometry
| parallax = 51.50
| p_error = 0.23
}}
{{Starbox orbit
| period_unitless = 1.767 days
| eccentricity = 0.065
| k1 = 10.64
}}
{{Starbox detail
| component1 = α Tri A
| luminosity =
| metal_fe = −0.09 to 0.00
| component2 = α Tri B
}}
{{Starbox catalog
| names = Mothallah, Ras al Muthallah, Caput Trianguli, α Trianguli, 2 Trianguli, HR 544, HD 11443, BD+28°312, FK5 64, HIP 8796, SAO 74996.
}}
{{Starbox reference
|Simbad=alf+Tri
}}
{{Starbox end}}
Alpha Trianguli (α Trianguli, abbreviated Alpha Tri, α Tri) is a spectroscopic binary star in the constellation of Triangulum. Based on parallax measurements obtained during the Hipparcos mission, it is approximately {{Convert|63.3|ly|pc|abbr=off|lk=on}} distant from the Sun. The brighter or primary component is named Mothallah {{IPAc-en|m|@|'|θ|æ|l|@}}.
Nomenclature
α Trianguli (Latinised to Alpha Trianguli) is the system's Bayer designation.
The system bore the traditional names Ras al Muthallah or Mothallah and Caput Trianguli derived from the Arabic رأس المثلث' raʼs al-muthallath "the head of the triangle" and its Latin translation. The International Astronomical Union Working Group on Star Names (WGSN) has approved the name Mothallah for this star. For members of multiple star systems, and where a component letter (e.g. from the Washington Double Star Catalog) is not explicitly shown in the namelist, the WGSN says that the name should be understood to be attributed to the visually brightest component by visual brightness.
In combination with Beta Trianguli, these stars were called Al Mīzān, which is Arabic for "The Scale Beam".
In Babylonian astronomy, Alpha Trianguli is listed as UR.BAR.RA "The Wolf", bearing the epithet "the seeder of the plough" in the MUL.APIN, listed after "The Plough", the name for a constellation formed of Triangulum plus Gamma Andromedae.
Properties
File:AlphaTriLightCurve.png for Alpha Trianguli, plotted from TESS data]]
Estimates of the combined stellar classification for this system range from F5III to F6IV, with the luminosity class of 'IV' or 'III' indicating the primary component is a subgiant or giant star, respectively. It is a member of a close binary system—a spectroscopic binary—whose components complete an orbit about their center of mass once every 1.736 days. Because the primary star is rotating rapidly, it has assumed the shape of an oblate spheroid. The ellipsoidal profile of the star, as viewed from Earth, varies over the course of an orbit causing the luminosity to vary in magnitude during the same period. Such stars are termed ellipsoidal variables. Within a few million years, as the primary continues to evolve into a red giant star, the system may become a semi-detached binary with the Roche lobe becoming filled to overflowing.
The mean apparent magnitude of +3.42 for this pair is bright enough to be readily seen with the naked eye. It forms the second brightest star or star system in this generally faint constellation, following Beta Trianguli. The effective temperature of the primary's outer envelope is 6,288 K, giving it a yellow-white hue typical of F-type stars. It has a mean radius about three times the radius of the Sun. The system is an estimated 1.6 billion years old.
References
{{Reflist|30em|refs=
{{cite book | first1=Robert A. | last1=Garfinkle | title=Star-Hopping: Your Visa to Viewing the Universe | publisher=Cambridge University Press | date=1997 | isbn=0-521-59889-3 | page=238 | url=https://books.google.com/books?id=40JzBYGREL0C&pg=PA238 }}
| url=https://www.iau.org/science/scientific_bodies/working_groups/280/
| title=IAU Working Group on Star Names (WGSN)
| publisher=International Astronomical Union
| accessdate=22 May 2016 }}
{{cite journal | last=Wilson | first=Ralph Elmer | date=1953 | title=General catalogue of stellar radial velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution of Washington | bibcode=1953GCRV..C......0W }}
{{cite simbad | title=V* alf Tri -- Ellipsoidal variable Star | accessdate=2011-12-12 }}
{{cite web|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |url-status=dead |archiveurl=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=March 18, 2012 }}
{{cite journal |last1=Fuhrmann |first1=Klaus |title=Nearby stars of the Galactic disc and halo - IV |journal=Monthly Notices of the Royal Astronomical Society |volume=384 |issue=1 |pages=173–224 |date=February 2008 |doi=10.1111/j.1365-2966.2007.12671.x |bibcode=2008MNRAS.384..173F |doi-access=free}}
}}
External links
- {{citation|first1=James B. |last1=Kaler |work=Stars |title=MOTHALLAH (Alpha Trianguli) |publisher=University of Illinois |url=http://www.astro.uiuc.edu/~kaler/sow/mothallah.html |accessdate=2011-12-12 |url-status=dead |archiveurl=https://web.archive.org/web/20080704201929/http://www.astro.uiuc.edu/~kaler/sow/mothallah.html |archivedate=2008-07-04 }}
{{Stars of Triangulum}}
{{Authority control}}
{{DEFAULTSORT:Alpha Trianguli}}
Category:Spectroscopic binaries