39 Arietis

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39 Arietis
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension 02h 47m 54.54142s[1]
Declination +29° 14′ 49.6132″[1]
Apparent magnitude (V) 4.514[2]
Spectral type K1.5 III[3]
U−B color index +1.083[2]
B−V color index +1.118[2]
R−I color index 0.58
Radial velocity (Rv) –15.53 ± 0.14[4] km/s
Proper motion (μ) RA: +149.47 ± 0.25[1] mas/yr
Dec.: –127.05 ± 0.18[1] mas/yr
Parallax (π) 19.01 ± 0.21[1] mas
Distance 172 ± 2 ly
(52.6 ± 0.6 pc)
Mass 1.6[5] M
Radius 11.1 ± 0.8[3] R
Luminosity 56[4] L
Surface gravity (log g) 2.7[4] cgs
Temperature 4,603[4] K
Metallicity [Fe/H] –0.02[4] dex
Rotational velocity (v sin i) 4.5[4] km/s
Other designations
Lilii Borea, BD+28° 462, HD 17361, HIP 13061, HR 824, SAO 75578.[6]
Database references

39 Arietis (abbreviated 39 Ari), also named Lilii Borea,[7] is a star in the northern constellation of Aries. It is visible to the naked eye with an apparent visual magnitude of +4.5.[2] The distance to this star, as determined from an annual parallax shift of 19.01 mas,[1] is approximately 172 light-years (53 parsecs).


39 Arietis is the star's Flamsteed designation. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[8] to catalog and standardize proper names for stars. The WGSN approved the name Lilii Borea for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[7]

In Chinese, 胃宿 (Wèi Su), meaning Stomach, refers to an asterism consisting of 39 Arietis, 35 Arietis and 41 Arietis.[9] Consequently, 39 Arietis itself is known as 胃宿二 (Wèi Su èr, English: the Second Star of Stomach).[10]


39 Arietis is a giant star with a stellar classification of K1.5 III.[3] It is currently at an evolutionary stage known as the red clump, indicating that it is generating energy through the fusion of helium at its core.[5] It has 1.6[5] times the mass of the Sun, but its outer envelope has expanded to around 11[3] times the Sun's radius. It shines with 56 times the luminosity of the Sun.[4] This energy is being radiated into outer space from its outer atmosphere at an effective temperature of 4,603 K,[4] giving it the cool orange-hued glow of a K-type star.[11]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Oja, T., "UBV photometry of stars whose positions are accurately known. III", Astronomy and Astrophysics Supplement Series, 65 (2): 405–4. 
  3. ^ a b c d Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal, 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114 
  4. ^ a b c d e f g h 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 Tautvaišienė, G.; et al. (December 2010), "C, N and O abundances in red clump stars of the Milky Way", Monthly Notices of the Royal Astronomical Society, 409 (3): 1213–1219, arXiv:1007.4064Freely accessible, Bibcode:2010MNRAS.409.1213T, doi:10.1111/j.1365-2966.2010.17381.x. 
  6. ^ "* 39 Ari". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-18. 
  7. ^ a b "Naming Stars". IAU.org. Retrieved 16 December 2017. 
  8. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  9. ^ (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.
  10. ^ (in Chinese) 白羊座
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16 

External links

  • Aladin previewer
  • Aladin sky atlas
  • HR 824
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