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Mu Herculis (μ Herculis) is a nearby quadruple
star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking ...
about 27.1 
light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
s from Earth in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...
Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the G ...
. Its main star, Mu Herculis A is fairly similar to the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrare ...
although more highly
evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
with a
stellar classification In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting th ...
of G5 IV. Since 1943, the
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of color ...
of this star has served as one of the stable anchor points by which other stars are classified. Its mass is about 1.1 times that of the Sun, 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 Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
as ''Cubitum Sinistrum Ingeniculi'', meaning ''the left elbow of kneeling man''. In
Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of v ...
, (), 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. Consequently, the
Chinese name Chinese names or Chinese personal names are names used by individuals from Greater China and other parts of the Chinese-speaking world throughout East and Southeast Asia (ESEA). In addition, many names used in Japan, Korea and Vietnam are often ...
for μ Herculis itself is (, en, the Third Star of Left Wall of Heavenly Market Enclosure), represent ''Jiuhe'' (九河, lit. meaning ''nine rivers''), possibly for
Jiujiang Jiujiang (), formerly transliterated Kiukiang or Kew Keang, is a prefecture-level city located on the southern shores of the Yangtze River in northwest Jiangxi Province, People's Republic of China. It is the second-largest prefecture-level city ...
, the prefecture-level city in Jiangxi, China, which is the same literally meaning with ''Jiuhe''. From this Chinese title, the name ''Kew Ho'' appeared.Star Name - R.H. Allen p. 238
/ref>


Star system

Mu Herculis is a quadruple star system. The brightest star is a well-studied G-type
subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution o ...
, whose parameters are precisely determined from
asteroseismology Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperatu ...
. 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 Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from 780 nm to 2500 nm). Typical applications include medical and physiological diagnostics and research incl ...
. The companion star is a
red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave (TV channel), Dave since 2009, gaining a ...
with a
spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting th ...
of M4V and a mass of . This pair is also known as Mu1 Herculis. The secondary component, also known as Mu2 Herculis, consists of a pair of stars that orbit about each other with a period of about 43 years. Mu Herculis A and the binary pair B-C are separated by some 35 arcseconds. 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.


See also

* List of star systems within 25–30 light-years


References


External links

*Jim Kaler's Stars, University of Illinois
MU HER (Mu Herculis)
*SolStation

{{DEFAULTSORT:Mu Herculis Hercules (constellation) 4 G-type subgiants M-type main-sequence stars Herculis, Mu Herculis, Mu Herculis, 086 086974 6623 0695 Durchmusterung objects 161797