61 Ursae Majoris

61 Ursae Majoris (61 UMa) is an orange-yellow G8 main-sequence star in the constellation Ursa Major. It is somewhat smaller and fainter than the Sun, and can just barely be seen by the unaided eye (based on a magnitude limit of 6). Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[12]

61 Ursae Majoris
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension  11h 41m 03.0153s[1]
Declination +34° 12′ 05.888″[1]
Apparent magnitude (V) 5.35[2]
Characteristics
Spectral type G8V[3]
U−B color index +0.27[4]
B−V color index +0.69[4]
R−I color index 0.37
Variable type Suspected
Astrometry
Radial velocity (Rv)−5.4[5] km/s
Proper motion (μ) RA: −13.95[1] mas/yr
Dec.: −380.46[1] mas/yr
Parallax (π)104.81 ± 0.72[1] mas
Distance31.1 ± 0.2 ly
(9.54 ± 0.07 pc)
Absolute magnitude (MV)5.53±0.006[6]
Details
Mass0.85[7] M☉
Radius0.940 ± 0.010[8] R☉
Luminosity0.609 ± 0.009[8] L☉
Surface gravity (log g)4.69[2] cgs
Temperature5,270 ± 32[8] K
Metallicity [Fe/H]+0.03[2] dex
Rotation17.1 days[9]
Rotational velocity (v sin i)8[10] km/s
Age0.8–1.2[11] Gyr
Other designations
BD+35° 2270, FK5 1300, GCTP 2699.00, GJ 434, HD 101501, HIP 56997, HR 4496, LTT 13200, SAO 62655, NSV 5291.
Database references
SIMBADdata

No substellar companions have been observed in orbit around this star, and it appears to lack a dust ring as is found around some comparable stars. It lies near the same line of sight as the sub-giant star HD 101212, although it is unclear whether these two stars are gravitationally bound or even in physical proximity.

The space velocity components of this star are [U, V, W] = [+8, −16, −4] km/s. It is orbiting the galaxy at a mean distance of 7.9 kpc (26×10^3 ly) from the core with an eccentricity of 0.06.[13]

See also
  • 61 Ursae Majoris in fiction

References
  1. Perryman, M. A. C.; et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. Cornide, M.; Rego, M. (October 1984). "Iron abundances in G dwarfs". Astrophysics and Space Science. 105 (1): 55–65. Bibcode:1984Ap&SS.105...55C. doi:10.1007/BF00651207.
  3. Wilson, O. C. (November 1962). "Relationship Between Colors and Spectra of Late Main-Sequence Stars". Astrophysical Journal. 136: 793. Bibcode:1962ApJ...136..793W. doi:10.1086/147437.
  4. Johnson, H. L.; Morgan, W. W. (1953). "Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas". Astrophysical Journal. 117: 313–352. Bibcode:1953ApJ...117..313J. doi:10.1086/145697.
  5. Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  6. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73.
  7. Takeda, G.; et al. (2007). "Stellar parameters of nearby cool stars. II. Physical properties of ~1000 cool stars from the SPOCS catalog". Astrophysical Journal Supplement Series. 168: 297–318. arXiv:astro-ph/0607235. Bibcode:2007ApJS..168..297T. doi:10.1086/509763. Note: see VizieR catalogue J/ApJS/168/297.
  8. Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101. See Table 10.
  9. Maldonado, J.; et al. (October 2010), "A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups", Astronomy and Astrophysics, 521: A12, arXiv:1007.1132, Bibcode:2010A&A...521A..12M, doi:10.1051/0004-6361/201014948
  10. Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1). Bibcode:1970CoAsi.239....1B.
  11. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785.
  12. Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
  13. de Mello, G. F. Porto; del Peloso, E. F.; Ghezzi, L. (2006). "Astrobiologically interesting stars within 10 parsecs of the Sun". Astrobiology. 6 (2): 308–331. arXiv:astro-ph/0511180. Bibcode:2006AsBio...6..308P. doi:10.1089/ast.2006.6.308. PMID 16689649. Retrieved 2008-01-17.
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