Kappa Herculis (κ Her, κ Herculis) is a double star

Double star

In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...

 in the constellation

Constellation

In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Hercules

Hercules (constellation)

Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today...

. Traditional names that have been attributed to the star are "Marfik", "Marfak" or "Marsic", all of which come from the Arabic لمرفق Al-Mirfaq meaning "the elbow", a name (or some derivivation of which) it shares with Lambda Ophiuchi

Lambda Ophiuchi

Lambda Ophiuchi is a binary star system in the constellation Ophiuchus. It has the traditional name Marfik ....

.

Properties

Kappa Herculis is a giant star

Giant star

A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...

 with stellar classification

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 G8III. With a mass of 3.0 M_☉

Solar mass

The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

 and radius that is 16 R_☉, the star boasts a total bolometric

Bolometer

A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley...

 luminosity that is 150 L_☉. Its apparent magnitude

Apparent magnitude

The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...

 has been recently recalibrated at 5.1628. The Hipparcos

Hipparcos

Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

 mission estimated its distance at roughly 120 parsec

Parsec

The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....

s from Earth, or 390 ± 20 light years away.

Etymology

In Chinese

Chinese language

The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...

, , meaning Right Wall of Heavenly Market Enclosure

Heavenly Market enclosure

Tian Shi Yuan, the Heavenly Market Enclosure , is one of the San Yuan or Three enclosures. Stars and constellations of this group are visible during late summer and early autumn in the Northern Hemisphere . The summer triangle lies directly to the northwest.-Asterisms:The asterisms are :...

, refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of κ Herculis, β Herculis

Beta Herculis

Beta Herculis , which also has the name Kornephoros, is the brightest star in the constellation of Hercules. It has an apparent visual magnitude which varies between 2.76 and 2.81.Although β Herculis appears to the naked eye to be a single star, W. W...

, γ Herculis

Gamma Herculis

Gamma Herculis is a magnitude 3.74 binary star in the constellation Hercules. It is a giant star with a stellar classification of A9III that is located at a distance of about 195 light years from the Earth.-Name:...

, γ Serpentis, β Serpentis

Beta Serpentis

Beta Serpentis is a star system in the constellation Serpens, in its head . It was a member of indigenous Arabic asterism al-Nasaq al-Sha'āmī, "the Northern Line" of al-Nasaqān "the Two Lines", along with β Her , γ Her and γ Ser .According to the catalogue of stars in the Technical Memorandum...

, δ Serpentis

Delta Serpentis

Delta Serpentis is a star system in the constellation Serpens, in its head . It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines"., along with α Ser , ε Ser , δ Oph , ε Oph , ζ Oph and γ Oph .According to the...

, α Serpentis

Alpha Serpentis

Alpha Serpentis is a triple star system in the constellation Serpens, in its head . Alpha Serpentis has the proper names Unukalhai, from the Arabic عنق الحية ‘Unuq al-Ħayyah "the Serpent's Neck", and Cor Serpentis from the Latin "the Heart of the Serpent"...

, ε Serpentis

Epsilon Serpentis

Epsilon Serpentis is a star in the constellation Serpens, in its head .It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines"., along with α Ser , δ Ser , δ Oph , ε Oph , ζ Oph and γ Oph .According to the...

, δ Ophiuchi

Delta Ophiuchi

Delta Ophiuchi is a star in the constellation Ophiuchus. It has the traditional name Yed Prior ....

, ε Ophiuchi

Epsilon Ophiuchi

Epsilon Ophiuchi is a star in the constellation Ophiuchus. It has the traditional name Yed Posterior ....

 and ζ Ophiuchi

Zeta Ophiuchi

Zeta Ophiuchi is a star located in the constellation of Ophiuchus. It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines"., along with α Ser , δ Ser , ε Ser , δ Oph , ε Ser and γ Oph .According to the catalogue of stars...

 . Consequently, κ Herculis itself is known as , represent the state Jin (趙) (or Tsin)., together with 36 Capricorni

36 Capricorni

36 Capricorni is a star in the constellation Capricornus. 36 Capricorni is a yellow G-type giant with an apparent magnitude of +4.50. It is approximately 179 light years from Earth.-Chinese Name:...

 in Twelve States

Girl (Chinese constellation)

The Girl mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise.- Asterisms :...

(asterism).

See also

• Lists of stars in the constellation Hercules
• Class G Stars
• Giant star
  Giant star
  A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
  
  
• Double star
  Double star
  In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
  
  

External links

• Jim Kaler's Stars, University of Illinois: MARSIC (Kappa Herculis)
• Hercules constellation map showing: κ Herculis