Lambda Herculis

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Lambda Herculis
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 17h 30m 44.3098s[1]
Declination +26° 06′ 38.324″[1]
Apparent magnitude (V) 4.41[2]
Spectral type K3.5III[3]
U−B color index +1.68[4]
B−V color index +1.44[4]
Radial velocity (Rv)−26.51[5] km/s
Proper motion (μ) RA: +18.782[1] mas/yr
Dec.: +16.184[1] mas/yr
Parallax (π)8.2943 ± 0.0921 mas[1]
Distance393 ± 4 ly
(121 ± 1 pc)
Absolute magnitude (MV)−0.86[6]
Mass1.18[7] M
Radius40[8] R
Luminosity400[8] L
Surface gravity (log g)1.30[7] cgs
Temperature4,063 - 4,079[8] K
Metallicity [Fe/H]0.023[7] dex
Rotational velocity (v sin i)<1.5[9] km/s
Age3.98 or 7.23[8] Gyr
Other designations
λ Her, 76 Herculis, BD+26°3034, FK5 1460, HD 158899, HIP 85693, HR 6526, SAO 249461[10]
Database references

Lambda Herculis (λ Herculis. abbreviated Lambda Her, λ Her), formally named Maasym /ˈməsɪm/,[11] is a star in the constellation of Hercules. From parallax measurements taken during the Gaia mission, it is approximately 393 light-years from the Sun.


λ Herculis (Latinised to Lambda Herculis) is the star's Bayer designation.

It bore the traditional name Maasym, from the Arabic مِعْصَم miʽṣam "wrist". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalogue and standardize proper names for stars. The WGSN approved the name Maasym for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[11]

In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China and which is marking the left borderline of the enclosure, consisting of Lambda Herculis, Delta Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Theta1 Serpentis, Eta Serpentis, Nu Ophiuchi, Xi Serpentis and Eta Ophiuchi.[13] Consequently, the Chinese name for Lambda Herculis itself is 天市左垣二 (Tiān Shì Zuǒ Yuán èr, English: the Second Star of Left Wall of Heavenly Market Enclosure), and represents the state Zhao (or Chaou (趙)),[14][15] together with 26 Capricorni and 27 Capricorni ("m Capricorni" in R.H.Allen version[16]) in Twelve States (asterism).


Lambda Herculis has an apparent magnitude of 4.4. It has been listed as a standard star for the spectral class spectral class K3.5III,[3] indicating that it is a red giant with a temperature of about 4,000 K. Visually it has an absolute magnitude of −0.86, meaning it is nearly 200 times brighter than the sun, but its bolometric luminosity across all wavelengths is over 400 L. It is unclear whether the star is on the red giant branch and fusing hydrogen in a shell or on the horizontal branch (red clump) and fusing helium in its core. As a horizontal-branch star it would be about seven billion years old, but as a red-giant-branch star it would only be about four billion years old.[8]

In 1783, English-German astronomer William Herschel described the solar apex, the point in sky towards which the Solar System is moving; using data from double stars, he identified this position as close to Lambda Herculis. Today it is known the solar apex is not so close to this star, however it is only 10° away from the position currently accepted (in Hercules, southwest of Vega).[17][18][19]


  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ 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". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. ^ a b Johnson, H. L.; Iriarte, B.; Mitchell, R. I.; Wisniewskj, W. Z. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  5. ^ Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (January 2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165–186. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
  6. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  7. ^ a b c Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevič, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; de Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN 0004-6361.
  8. ^ a b c d e Reffert, Sabine; et al. (2015). "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity". Astronomy and Astrophysics. 574A (2): 116–129. arXiv:1412.4634. Bibcode:2015A&A...574A.116R. doi:10.1051/0004-6361/201322360. hdl:10722/215277. S2CID 59334290.
  9. ^ De Medeiros, J. R.; Alves, S.; Udry, S; Andersen, J; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars. V. Southern stars". Astronomy & Astrophysics. 561: 27. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. S2CID 54046583.
  10. ^ "lam Her -- Variable Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-07-03.
  11. ^ a b "Naming Stars". Retrieved 16 December 2017.
  12. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  13. ^ (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.
  14. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2011-01-30 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  15. ^ (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived 2008-09-24 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ^ Star Names - R.H.Allen p.142
  17. ^ Lankford, John (1997). History of astronomy: an encyclopedia. Garland encyclopedias in the history of science. Vol. 1. Taylor & Francis. p. 258. ISBN 0-8153-0322-X.
  18. ^ Herschel, William (1783). "On the Proper Motion of the Sun and Solar System; With an Account of Several Changes That Have Happened among the Fixed Stars since the Time of Mr. Flamstead [sic]". Philosophical Transactions of the Royal Society of London. 73: 247–83. doi:10.1098/rstl.1783.0017. JSTOR 106492. S2CID 186213288.
  19. ^ Kaler, Jim. "Furud". Retrieved 2017-04-26.