Sigma1 Ursae Majoris
Solitary star in the constellation Ursa Major
Sigma1 Ursae Majoris (σ1 UMa ) is the Bayer designation for a solitary[ 8] star in the northern circumpolar constellation of Ursa Major . With an apparent visual magnitude of 5.14[ 2] it is faintly visible to the naked eye on dark nights. Based upon an annual parallax shift of 6.26 mas ,[ 1] it is located roughly 520 light years from the Sun . At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.06[ 3] due to interstellar dust .
This is an evolved K-type giant star with a stellar classification of K5 III.[ 3] It is a suspected variable with an amplitude of 0.03 magnitude.[ 3] The measured angular diameter of the star after correcting for limb darkening is 2.67± 0.04 mas ,[ 9] which, at the estimated distance of this star, yields a physical size of about 46 times the radius of the Sun .[ 5] The star is radiating around 560[ 3] times the solar luminosity from its outer atmosphere at an effective temperature of 3,940 K.[ 6]
Naming
With π1 , π2 , σ2 , ρ , A and d , it composed the Arabic asterism Al Ṭhibā᾽ , the Gazelle.[ 10] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars , Al Ṭhibā were the title for seven stars : A as Althiba I , this star (π1 ) as Althiba II , π2 as Althiba III , ρ as Althiba IV , this star (σ1 ) as Althiba V , σ2 as Althiba VI , and d as Althiba VII .[ 11]
References
^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics , 474 (2): 653–664, arXiv :0708.1752 , Bibcode :2007A&A...474..653V , doi :10.1051/0004-6361:20078357 , S2CID 18759600 .
^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data , SIMBAD , Bibcode :1986EgUBV........0M .
^ a b c d e f g Groenewegen, M. A. T. (April 2012), "Infrared excess around nearby red giant branch stars and Reimers law", Astronomy & Astrophysics , 540 : 21, Bibcode :2012A&A...540A..32G , doi :10.1051/0004-6361/201118287 , A32.
^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics , 546 : 14, arXiv :1208.3048 , Bibcode :2012A&A...546A..61D , doi :10.1051/0004-6361/201219219 , S2CID 59451347 , A61.
^ a b Lang, Kenneth R. (2006), Astrophysical formulae , Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser , ISBN 3-540-29692-1 . The radius (R* ) is given by:
2
⋅ ⋅ -->
R
∗ ∗ -->
=
(
159.7
⋅ ⋅ -->
2.67
⋅ ⋅ -->
10
− − -->
3
)
AU
0.0046491
AU
/
R
⨀ ⨀ -->
≈ ≈ -->
91.7
⋅ ⋅ -->
R
⨀ ⨀ -->
{\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(159.7\cdot 2.67\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 91.7\cdot R_{\bigodot }\end{aligned}}}
^ a b c d Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics , 515 : A111, arXiv :1004.1069 , Bibcode :2010A&A...515A.111S , doi :10.1051/0004-6361/201014247 , S2CID 118362423 .
^ "sig01 UMa" . SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2017-02-25 .{{cite web }}
: CS1 maint: postscript (link )
^ 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 .
^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics , 431 (2): 773–777, Bibcode :2005A&A...431..773R , doi :10.1051/0004-6361:20042039 .
^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings , New York: G. E. Stechert, p. 444
^ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF) , Jet Propulsion Laboratory, California Institute of Technology.