Mu Ursae Majoris

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Mu Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings

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]
Database references

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