Sigma Boötis

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σ Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 34m 40.8171s
Declination +29° 44′ 42.468″
Apparent magnitude (V) 4.46
Spectral type F2V
U−B color index -0.08
B−V color index 0.36
R−I color index 0.19
Variable type Variable star
Radial velocity (Rv) 0.2 km/s
Proper motion (μ) RA: 188.32 mas/yr
Dec.: 132.72 mas/yr
Parallax (π) 64.66 ± 0.72 mas
Distance 50.4 ± 0.6 ly
(15.5 ± 0.2 pc)
Absolute magnitude (MV) 3.52[1]
Radius 1.431 ± 0.023[2] R
Luminosity 3.461 ± 0.042[2] L
Surface gravity (log g) 4.30[1] cgs
Temperature 6,594 ± 55[2] K
Age 1.7[3] Gyr
Other designations
28 Boötis, HR 5447, HD 128167, Gl 557, BD+30°2536, FK5 1380, HIP 71284, SAO 83416, GC 19659, CCDM 14347+2945.
Database references
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)
Database references

Sigma Boötis (σ Boo, σ Boötis) is a star in the constellation Boötes.

Sigma Boötis is a yellow-white F-type main sequence dwarf with an apparent magnitude of +4.47. It is approximately 50.4 light years from Earth.

In Chinese, 梗河 (Gěng Hé), meaning Celestial Lance, refers to an asterism consisting of σ Boötis, ε Boötis and ρ Boötis.[4] Consequently, σ Boötis itself is known as 梗河二 (Gěng Hé èr, English: the Second Star of Celestial Lance.)[5]

Located to the southeast of Rho Boötis, the fusing dwarf Sigma may at first appear as a naked-eye double, but the angular proximity with Rho is merely line-of-sight. Like many of its spectral class, Sigma is apparently a variable of the Delta Scuti variety, which vary subtly with multiple periods of hours.


  1. ^ a b Paunzen, E.; et al. (July 2014), "Investigating the possible connection between λ Bootis stars and intermediate Population II type stars", Astronomy & Astrophysics, 567: 8, arXiv:1406.3936Freely accessible, Bibcode:2014A&A...567A..67P, doi:10.1051/0004-6361/201423817, A67. 
  2. ^ a b c 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:1112.3316Freely accessible, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101 . See Table 10.
  3. ^ Decin, G.; et al. (November 2003), "Age Dependence of the Vega Phenomenon: Observations", The Astrophysical Journal, 598 (1): 636–644, arXiv:astro-ph/0308294Freely accessible, Bibcode:2003ApJ...598..636D, doi:10.1086/378800 
  4. ^ (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.
  5. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 29 日

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