Mu Ursae Majoris

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Mu Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Cercle rouge 100%.svg

Location of μ Ursae Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 10h 22m 19.744s[1]
Declination +41° 29′ 58.28″[1]
Apparent magnitude (V) +3.06[2]
Spectral type M0 IIIab[2]
U−B color index +1.90[3]
B−V color index +1.59[3]
Radial velocity (Rv) –21.30 ± 1.66[4] km/s
Proper motion (μ) RA: –81.47[5] mas/yr
Dec.: +35.34[5] mas/yr
Parallax (π) 14.16 ± 0.54[5] mas
Distance 230 ± 9 ly
(71 ± 3 pc)
Period (P) 230.089 ± 0.039 days
Eccentricity (e) 0.061 ± 0.022
Periastron epoch (T) 2425577.03 JD
Argument of periastron (ω)
236.4 ± 17.4°
Semi-amplitude (K1)
7.43 ± 0.16 km/s
Radius 75[7] R
Luminosity 977[7]–1,200[4] L
Surface gravity (log g) 1.0[4] cgs
Temperature 3,899[4] K
Metallicity [Fe/H] +0.00[8] dex
Rotational velocity (v sin i) 7.5[4] km/s
Other designations
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.[9]

Mu Ursae Majoris (Mu UMa, μ Ursae Majoris, μ UMa) is a star in the constellation Ursa Major. An apparent visual magnitude of +3.06[2] places it among the brighter members of the constellation. Parallax measurements give an estimated distance of roughly 230 light-years (71 parsecs) from Earth, with a margin of error of 4%.[5] This star has the proper name Tania Australis (formerly Tania australis[10])

Mu Ursae Majoris is an evolved star that is currently in the red giant stage with a stellar classification of M0 IIIab.[2] It has expanded to 75[7] times the radius of the Sun whilst the outer atmosphere has cooled to an effective temperature of 3,899 K,[4] giving it the orange-red hued glow of an M-type star.[11] Estimates of the luminosity range from 977[7]–1,200[4] times that of the Sun. It is classified as a semiregular variable star and its brightness varies from magnitude 2.99m to 3.33m.

This is a spectroscopic binary star system with a companion a mere 1.5[citation needed] AU from the primary with an orbital period of 230 days.[6]

Name and etymology[edit]

  • The traditional name Tania' (share with λ UMa) comes from the Arabic phrase Al Fiḳrah al Thānia "the Second Spring (of the Gazelle)".[12] The term Australis meaning "the south side" in Latin.
  • In Chinese, 三台 (Sān Tái), meaning Three Steps, refers to an asterism consisting of μ Ursae Majoris, ι Ursae Majoris, κ Ursae Majoris, λ Ursae Majoris, ν Ursae Majoris and ξ Ursae Majoris. Consequently, μ Ursae Majoris itself is known as 三台四 (Sān Tái sì, English: the Fourth Star of Three Steps) and 中台二 (Zhōng Tái èr, English: Star of Second Middle Step).[13]


  1. ^ a b Frosty Drew Observatory & Sky Theatre — Tania Australis
  2. ^ a b c d Mallik, Sushma V. (December 1999), "Lithium abundance and mass", Astronomy and Astrophysics 352: 495–507, Bibcode:1999A&A...352..495M 
  3. ^ a b 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. 
  4. ^ a b c d e f g Massarotti, Alessandro et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209 
  5. ^ a b c d van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752v1, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357  Note: see VizieR catalogue I/311.
  6. ^ a b Jackson, E. S.; Shane, W. W.; Lynds, Beverly T. (May 1957), "The Orbits of the Spectroscopic Binaries Omicron Tauri, Xi Cancri, and Mu Ursae Majories", Astrophysical Journal 125: 712, Bibcode:1957ApJ...125..712J, doi:10.1086/146345 
  7. ^ a b c d Jorissen, A. et al. (May 2009), "Spectroscopic binaries among Hipparcos M giants. III. The eccentricity - period diagram and mass-transfer signatures", Astronomy and Astrophysics 498 (2): 489–500, arXiv:0901.0938, Bibcode:2009A&A...498..489J, doi:10.1051/0004-6361/200810703 
  8. ^ Mallik, Sushma V. (October 1998), "Chromospheric activity in cool stars and the lithium abundance", Astronomy and Astrophysics 338: 623–636, Bibcode:1998A&A...338..623M 
  9. ^ "34 UMa -- Spectroscopic binary", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-03-05 
  10. ^ Piazzi, G. (1814), The Palermo Catalogue, Palermo 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  12. ^ Richard Hinckley Allen :Star Names — Their Lore and Meaning - Ursa Major, the Greater Bear
  13. ^ (Chinese) (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日