51 Andromedae

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51 Andromedae
Diagram showing star positions and boundaries of the Andromeda constellation and its surroundings
Cercle rouge 100%.svg
Arc position of this star (red circled), north-west of Andromeda Galaxy viewed from earth.
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  01h 37m 59.56074s[1]
Declination +48° 37′ 41.5798″[1]
Apparent magnitude (V) 3.57[2]
Spectral type K3- III CN0.5[3]
U−B color index +1.44[2]
B−V color index +1.28[2]
Radial velocity (Rv)18.41[4] km/s
Proper motion (μ) RA: +61.334[1] mas/yr
Dec.: -113.100[1] mas/yr
Parallax (π)19.2489 ± 0.4077[1] mas
Distance169 ± 4 ly
(52 ± 1 pc)
Absolute magnitude (MV)−0.04[5]
Mass1.75±0.15 M
Radius21.30±0.21 R
Luminosity142.1±7.6 L
Surface gravity (log g)2.01 cgs
Temperature4,951±64 K
Metallicity [Fe/H]0.07 dex
Age1.70±0.40 Gyr
Other designations
υ Per, 51 And, BD+47° 467, HD 9927, HIP 7607, HR 464, SAO 37375[7]
Database references

51 Andromedae, abbreviated 51 And and formally named Nembus /ˈnɛmbəs/,[8] is the 5th brightest star in the northern constellation of Andromeda, very slightly dimmer than the Andromeda Galaxy also being of 4th magnitude. It is an orange K-type giant star with an apparent magnitude of +3.59 and is about 169 light-years from the Earth/solar system. It is traditionally depicted as one of the two northern, far upper ends of the mythological, chained-to-the-rocks princess, the other being binary star system Gamma Andromedae.

At an estimated age of 1.7 billion years, this is an evolved red giant star with a stellar classification of K3- III CN0.5.[3] The suffix notation indicates a mild enhancement of cyanogen absorption lines in its spectrum. This star has 1.8 times the mass of the Sun and it has expanded to 21.3 times the Sun's radius. It is radiating 142 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,951 K.[6]


51 Andromedae is the star's Flamsteed designation. Ptolemy included this star in Andromeda in the Almagest. It was for a time moved into the greater form of Perseus envisioned by Johann Bayer as Upsilon Persei. Flamsteed oversaw its constellation reverting and the International Astronomical Union (IAU) made his 51 Andromedae its official designation in 1930.[9][10][11]

The star bore the name Nembus, of undetermined origin and meaning,[12] in Bayer's Uranometria (1603)[13] and Bode's star atlas Uranographia (1801).[14] In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN approved the name Nembus for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[8]

In Chinese, 天大將軍 (Tiān Dà Jiāng Jūn), meaning Heaven's Great General, refers to an asterism consisting of 51 Andromedae, Gamma Andromedae, Phi Persei, 49 Andromedae, Chi Andromedae, Upsilon Andromedae, Tau Andromedae, 56 Andromedae, Beta Trianguli, Gamma Trianguli and Delta Trianguli.[16] Consequently, the Chinese name for 51 Andromedae itself is 天大將軍三 (Tiān Dà Jiāng Jūn sān, English: the Third Star of Heaven's Great General.)[17]


  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. ^ Maldonado, J.; Villaver, E.; Eiroa, C. (2013). "The metallicity signature of evolved stars with planets". Astronomy & Astrophysics. 554: A84. arXiv:1303.3418. Bibcode:2013A&A...554A..84M. doi:10.1051/0004-6361/201321082.
  5. ^ Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440.
  6. ^ a b Baines, Ellyn K.; et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155, 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b.
  7. ^ "HD 9927". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 24 August 2018.
  8. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017.
  9. ^ "Ephemerides – Report of Commissions", Transactions of the International Astronomical Union, 4: 20, 1932
  10. ^ Allen, R. H. (1899). Star-names and Their Meanings. New York: G. E. Stechart., p.34.
  11. ^ Wagman, Morton (2003) Lost Stars p.240, McDonald and Woodward, Blacksburg, Virginia. ISBN 0-939923-78-5.
  12. ^ Allen, R. H. (1899). Star-names and Their Meanings. New York: G. E. Stechart. p.334
  13. ^ Scans of the plates of Uranometria by J. Bayer, 1603 Archived August 7, 2008, at the Wayback Machine @Linda Hall Library
  14. ^ Scan of the plates of Uranographia by J.E. Bode, 1801 @Ian Ridpath's Star Tales
  15. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  16. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  17. ^ (in Chinese) http://zh.wikipedia.org/zh-tw/%E5%A4%A9%E5%A4%A7%E5%B0%86%E5%86%9B%E4%B8%89

External links[edit]