Mu Boötis

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Mu Boötis
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 15h 24m 29.4278s
Declination +37° 22′ 37.8″
Apparent magnitude (V) 4.31[1] / 6.5
Spectral type F0V[1] + G1V
U−B color index 0.07 / 0.13
B−V color index 0.31 / 0.59
R−I color index 0.15 /
Radial velocity (Rv) -12.5 km/s
Proper motion (μ) RA: -147.68 mas/yr
Dec.: 84.69 mas/yr
Parallax (π) 26.96 ± 0.65 mas
Distance 121 ± 3 ly
(37.1 ± 0.9 pc)
Mu Boötis A
Mass 1.7[1] M
Radius 1.9[1] R
Luminosity 8[1] L
Surface gravity (log g) 4.14[1] cgs
Temperature 7,190 ± 140[1] K
Companion CCDM 15245+3722 C
Period (P) 260.1 yr
Semi-major axis (a) 1.463"
Eccentricity (e) 0.59
Inclination (i) 135.4°
Longitude of the node (Ω) 174.9°
Periastron epoch (T) 1865
Other designations
Alkalurops, Inkalunis, Icalurus, Clava, Venabulum, 51 Boötis, HR 5733+HR 5734, HD 137391+HD 137392, NN 3903+NN 3904, BD+37°2636+BD 37°2637, FK5 568, HIP 75411+HIP 75415, SAO 64686+SAO 64687, GC 20724+GC 20725, ADS 9626, CCDM 15245+3722.
Database references
Database references
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)
Database references

Mu Boötis (μ Boötis, abbreviated Mu Boo, μ Boo) is a triple star system in the constellation of Boötes. The primary is designated μ¹ Boötis and the secondary (itself a binary star), μ² Boötis. Mu Boötis had the traditional name Alkalurops, although the International Astronomical Union now regards that name as only applying to μ¹ Boötis.[2]

Mu Boötis is approximately 121 light-years from the Sun.


μ Boötis (Latinised to Mu Boötis) is the star's Bayer designation. It also bears the Flamsteed designation 51 Boötis.

The system's traditional name Alkalurops is from the Greek καλαύροψ kalaurops "a herdsman's crook or staff", with the Arabic prefix attached.[3] It has also been known as Inkalunis (from the Alfonsine tables), Clava (Latin 'the club') and Venabulum (Latin 'a hunting spear').[4]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[5] to catalogue and standardize proper names for stars. The WGSN approved the name Alkalurops for μ¹ Boötis on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[2]

It is known as 七公六, Qī Gōng liù (the Sixth Star of the Seven Excellencies) in Chinese.[6]


Illustration of Mu1,2 Boötis

μ¹ Boötis is a yellow-white F-type subgiant with an apparent magnitude of +4.31. Separated from the primary by 108 arcseconds in the sky is the binary star μ² Boötis, which has a combined spectral type of G1V and a combined brightness of +6.51 magnitudes. The components of μ² Boötis have apparent magnitudes of +7.2 and +7.8 and are separated by 2.2 arcseconds. They complete one orbit about their common centre of mass every 260 years.

See also[edit]


  1. ^ a b c d e f g Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M 
  2. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  3. ^ Allen, Richard H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 97. ISBN 0-486-21079-0. Retrieved 2016-09-15. 
  4. ^ Allen, Richard H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 105. ISBN 0-486-21079-0. Retrieved 2016-09-15. 
  5. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016. 
  6. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日

External links[edit]