Mu Ursae Majoris
{{short description|Binary star in the constellation Ursa Major}}
{{Starbox begin
| name = Mu Ursae Majoris
}}
{{Starbox image
| image = {{Location map|100x100
|AlternativeMap=Ursa Major IAU.svg
|caption=
|alt=Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
|width=320
|lat=43.25 |long=58.75
|mark=Cercle rouge 100%.svg | marksize=12
|float=center
}}| caption = Location of μ Ursae Majoris (circled)
}}
{{Starbox observe
| epoch = J2000
| dec = {{DEC|+41|29|58.2691}}
| constell = Ursa Major
}}
{{Starbox character
| type = AGB
}}
{{Starbox astrometry
| radial_v = {{val|-21.30|1.66}}
| parallax = 14.16
| p_error = 0.54
| absmag_v = {{Val|−1.11|0.083}}
}}
{{Starbox orbit
| period_unitless = 230.089 days
| eccentricity = 0.061
| inclination = 13.6
| axis = 0.0028
| periastron = 2425577.030 JD
| periarg = 236.4
| k1 = 7.40
}}
{{Starbox detail
| component1 = μ UMa A
| luminosity = 977–1,200
| age_myr =
| component2 = μ UMa B
}}
{{Starbox catalog
| names = Tania Australis, Alkafzah al Thaniyah, μ Ursae Majoris, μ UMa, Mu UMa, 34 Ursae Majoris, BD+42 2115, FK5 386, GC 14232, HD 89758, HIP 50801, HR 4069, PPM 51850, SAO 43310
}}
{{Starbox reference
|Simbad=HIP+50801
}}
{{Starbox end}}
Mu Ursae Majoris is a binary star in the constellation of Ursa Major, and possibly makes part of a triple star system. It has the proper name Tania Australis {{IPAc-en|'|t|ei|n|i|@|_|ɔː|'|s|t|r|ei|l|I|s}},{{cite book
|last1=Kunitzsch |first1=Paul
|last2=Smart |first2=Tim
|date = 2006 |edition = 2nd rev.
|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations
|publisher = Sky Pub |location = Cambridge, Massachusetts
|isbn = 978-1-931559-44-7
}} {{nowrap|Mu Ursae Majoris}} it is Bayer designation. An apparent visual magnitude of +3.06 places it among the brighter members of the constellation. Parallax measurements give a distance measurement of roughly {{Convert|230|ly|pc|abbr=off|lk=on}}, with a margin of error of 4%.
Stellar system
Mu Ursae Majoris is an evolved star that is currently in the red giant stage with a stellar classification of M0 IIIab. It has expanded to 75 times the radius of the Sun whilst the outer atmosphere has cooled to an effective temperature of 3,899 K, giving it the orange-red hued glow of an M-type star. Estimates of the luminosity range from 977–1,200 times that of the Sun. It is classified as a suspected variable star with a brightness variation from magnitude 2.99m to 3.33m.
This is a spectroscopic binary star system with a companion a mere 0.2 AU from the primary, with an orbital period of 230 days.
In addition to the inner pair, a proper motion companion has a 99% chance to be related to this system. It has a very low mass of just 0.1 solar masses, and a projected separation of 3,900 astronomical units.
Nomenclature
μ Ursae Majoris (Latinised to Mu Ursae Majoris) is the star's Bayer designation. It can be abbreviated to abbreviated {{nowrap|Mu UMa}} or {{nowrap|μ UMa}}.
It bore the traditional names Tania (shared with Lambda Ursae Majoris) and Tania Australis. Tania comes from the Arabic phrase {{Transliteration|ar|Al Fiḳrah al Thānia}} 'the Second Spring (of the Gazelle)'. and Australis (originally australis) is Latin for 'the south side'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Tania Australis for this star.
In Chinese, {{lang|zh|三台}} ({{lang|zh-Latn|Sān Tái}}), meaning Three Steps, refers to an asterism consisting of Mu Ursae Majoris, Iota Ursae Majoris, Kappa Ursae Majoris, Lambda Ursae Majoris, Nu Ursae Majoris and Xi Ursae Majoris. Consequently, the Chinese name for Mu Ursae Majoris itself is {{lang|zh|中台二}} ({{lang|zh-Latn|Zhōng Tái èr}}, {{langx|en|Star of Second Middle Step}}).
References
{{reflist|refs=
{{cite journal | display-authors=1
| last1=Park | first1=Sunkyung | last2=Kang | first2=Wonseok
| last3=Lee | first3=Jeong-Eun | last4=Lee | first4=Sang-Gak
| title=Wilson-Bappu Effect: Extended to Surface Gravity
| journal=The Astronomical Journal
| volume=146 | issue=4 | pages=73 | year=2013
| doi=10.1088/0004-6256/146/4/73 | bibcode=2013AJ....146...73P
| arxiv=1307.0592 | s2cid=119187733 }}
{{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 | archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | archive-date=March 18, 2012 | url-status=dead }}
| last1=Eggen | first1=Olin J.
| title=Asymptotic giant branch stars near the sun
| journal=Astronomical Journal
| volume=104 | issue=1 | pages=275–313 | date=July 1992
| doi=10.1086/116239 | bibcode=1992AJ....104..275E }}
}}
{{Stars of Ursa Major}}
Category:Asymptotic-giant-branch stars
Category:Spectroscopic binaries