Quadruple star system in the constellation Hercules
Mu Herculis
Historical view of the
Hercules constellation showing Mu Herculis (μ Her) as one of stars in the hero's elbow.
Observation data
Epoch J2000
Equinox J2000
Constellation
Hercules
μ Her Aab (μ1 Her)
Right ascension
17h 46m 27.52667s
[1]
Declination
+27° 43′ 14.4379″
[1]
Apparent magnitude (V)
3.417 ± 0.014
[1]
μ Her BC (μ2 Her)
Right ascension
17h 46m 25.079s
[2]
Declination
+27° 43′ 01.45″
[2]
Apparent magnitude (V)
10.2 / 10.7
[3]
Characteristics
μ Her Aab
Spectral type
G5IV
[4] / M4V
[5]
U−B
color index
+0.40
[6]
B−V
color index
+0.76
[6]
μ Her BC
Spectral type
M3.5V
[7]
U−B
color index
+1.00
[6]
B−V
color index
+1.50
[6]
Astrometry μ Her Aab
Radial velocity (Rv ) −17.07 ± 0.12
[8] km/s
Proper motion (μ)
RA: −291.66
[1]
mas /
yr
Dec.: −749.60
[1]
mas /
yr
Parallax (π) 120.33 ± 0.16
mas
[1]
Distance 27.11 ± 0.04
ly (8.31 ± 0.01
pc )
Absolute magnitude (MV ) 3.82 ± 0.02
[8] μ Her BC
Proper motion (μ)
RA: −343.35
[9]
mas /
yr
Dec.: −743.88
[9]
mas /
yr
Parallax (π) 119.8871 ± 0.2055
mas
[10]
Distance 27.21 ± 0.05
ly (8.34 ± 0.01
pc )
Absolute magnitude (MV ) +10.26
[11]
Position (relative to μ Her Aab)
[12]
Component μ Her BC
Angular distance 35
″
Orbit
[5] Primary μ Her Aa Companion μ Her Ab
Period (P) 98.9 ± 22.7
yr
Semi-major axis (a) 2.9 ± 0.3″
Eccentricity (e) 0.44 ± 0.06
Inclination (i) 62.82 ± 4.66°
Longitude of the node (Ω) 80.4 ± 1.7°
Periastron
epoch (T)
B 1921.1 ± 23.8
Argument of periastron (ω) (secondary)214 ± 16°
Semi-amplitude (K1 ) (primary)1.12 ± 0.10 km/s
Orbit
[3] Primary μ Her B Companion μ Her C
Period (P) 43.127 ± 0.013
yr
Semi-major axis (a) 1.385 ± 0.038″
Eccentricity (e) 0.1796 ± 0.0009
Inclination (i) 66.06 ± 0.15°
Longitude of the node (Ω) 60.07 ± 0.17°
Periastron
epoch (T) B 2008.335 ± 0.073
Argument of periastron (ω) (secondary)172.85 ± 0.64°
Details μ Her Aa
Mass 1.11 ± 0.01
[8]
M ☉
Radius 1.73 ± 0.02
[8]
R ☉
Luminosity 2.54 ± 0.08
[8]
L ☉
Surface gravity (log g ) 3.98 ± 0.10
[8]
cgs
Temperature 5560 ± 80
[8]
K
Metallicity [Fe/H]0.28 ± 0.07
[8]
dex
Rotation 52+3 −1 d
[8]
Rotational velocity (v sin i ) 1.7 ± 0.4
[8] km/s
Age 7.8+0.3 −0.4
[8]
Gyr μ Her Ab
Mass 0.32
[5]
M ☉
μ Her B
Mass 0.44
[13]
M ☉
Radius 0.60
[14]
R ☉
Luminosity 0.087
[14]
L ☉
Temperature 4,050
[14]
K
Metallicity [Fe/H]+0.21
[14]
dex μ Her C
Mass 0.39
[13]
M ☉
Other designations
86 Herculis,
Gl 695,
HR 6623,
BD +27° 2888,
HD 161797,
LHS 3326/3325,
LTT 15266,
SAO 85397,
FK5 667, LFT 1374,
GC 24138,
ADS 10786,
HIP 86974.
[15]
Database references
SIMBAD
μ Her Aab
μ Her BC
Mu Herculis (μ Herculis ) is a nearby quadruple
star system about 27.1
light years from Earth in the
constellation
Hercules . Its main star, Mu Herculis A is fairly similar to the
Sun although more highly
evolved with a
stellar classification of G5 IV. Since 1943, the
spectrum of this star has served as one of the stable anchor points by which other stars are classified.
[16] Its mass is about 1.1 times that of the Sun,
[8] and it is beginning to expand to become a giant.
Etymology
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket , this star was designated Marfak Al Jathih Al Aisr , which was translated into
Latin as Cubitum Sinistrum Ingeniculi , meaning the left elbow of kneeling man .
[17]
In
Chinese , 天市左垣 (Tiān Shì Zuǒ Yuán ), the
Left Wall of Heavenly Market Enclosure , refers to an asterism which represents eleven old states in China, marking the left borderline of the enclosure, consisting of μ Herculis,
δ Herculis ,
λ Herculis ,
ο Herculis ,
112 Herculis ,
ζ Aquilae ,
θ1 Serpentis ,
η Serpentis ,
ν Ophiuchi ,
ξ Serpentis and
η Ophiuchi .
[18] Consequently, the
Chinese name for μ Herculis itself is 天市左垣三 (Tiān Shì Zuǒ Yuán sān , English: the Third Star of Left Wall of Heavenly Market Enclosure ), represent Jiuhe (九河, lit. meaning nine rivers ), possibly for
Jiujiang , the prefecture-level city in Jiangxi, China, which is the same literally meaning with Jiuhe .
[19]
[20] From this Chinese title, the name Kew Ho appeared.
[21]
Star system
Mu Herculis is a quadruple star system. The brightest star is a well-studied
G-type
subgiant , whose parameters are precisely determined from
asteroseismology .
[8] It was believed to be a close binary with a low-mass stellar or a large substellar companion. This was confirmed when low-mass companion was resolved using
near-infrared spectroscopy .
[5] The companion star is a
red dwarf with a
spectral type of M4V and a mass of 0.32 M ☉ .
[5] This pair is also known as Mu1 Herculis.
The secondary component, also known as Mu2 Herculis,
[12] consists of a pair of stars that orbit about each other with a period of about 43 years.
[22] Mu Herculis A and the binary pair B-C are separated by some 35 arcseconds.
[15] The stars B and C, which orbit each other, are separated from each other by 1.385 arcseconds, and have a slightly eccentric orbit, at 0.1796.
[3]
See also
References
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External links