Mu Boötis

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μ1,2 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 Boo, μ Boötis) is a triple star system in the constellation Boötes. It has the traditional name Alkalurops (also Inkalunis, Clava, and Venabulum), and the Flamsteed designation 51 Boötis. Mu Boötis is approximately 121 light-years from Earth.

The name Alkalurops is from Greek καλαύροψ kalaurops "shepherd's staff", through the Arabic.

It is known as 七公六 (the Sixth Star of the Seven Excellencies) in Chinese.[2]

The primary component, μ¹ Boötis, is a yellow-white F-type subgiant with an apparent magnitude of +4.31.


Illustration of Mu1,2 Boötis

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. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日


NAME Right ascension Declination Apparent magnitude (V) Spectral type Database references
ADS 9626 B (ADS 9626 Aa) 15h 24m 36s +37° 23' Simbad
ADS 9626 C (CCDM J15245+3722BC) 15h 24m 30.8663s +37° 20' 50.28 6.5 G1V Simbad

External links[edit]