Theta Herculis (θ Her, θ Herculis) is a fourth-magnitude star

Star

A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 in the constellation 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...

. It has the traditional name Rukbalgethi Genubi.

Properties

Theta Her is a variable

Variable star

A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...

 K-type 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...

 K1IIaCN. In 1935, French astronomer P. Muller identified Theta Herculis as an irregular variable with a range of magnitudes

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...

 between 3.7 and 4.1 and a periodicity of roughly 8–9 days.

Etymology

In the Calendarium of Al Achsasi Al Mouakket, this star was designated Rekbet al Jathih al Aisr, which was translated into Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 as Genu Sinistrum Ingeniculi, meaning the left knee of the kneeling man. The traditional name Rukbalgethi Genubi that is encountered in various texts is etymologically similar to the stars Ruchbah

Delta Cassiopeiae

Delta Cassiopeiae is a star in the constellation Cassiopeia. It has the traditional names Ksora and Ruchbah, derived from the Arabic word ركبة rukbah meaning "knee"...

 and Zubenelgenubi

Alpha Librae

Alpha Librae is the second brightest star in the constellation Libra . It has the traditional name Zubenelgenubi. The name, from Arabic الزبن الجنوبي , means "southern claw" and was coined before Libra was recognized as distinct from Scorpius...

, the term "ruchbah" meaning "knee" while "genubi" signifies "southern"—hence the "southern knee", a meaning which can be gleaned more easily by looking at the accompanying constellation map.

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 Celestial Discipline

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 consisting of θ Herculis, ξ Coronae Borealis, ζ Herculis, ε Herculis

Epsilon Herculis

Epsilon Herculis is a fourth-magnitude spectroscopic binary star in the constellation Hercules. It has the traditional name Cujam....

, 59 Herculis, 61 Herculis, 68 Herculis and HD 160054. Consequently, θ Herculis itself is known as

See also

• Lists of stars in the constellation Hercules
• Class K Stars
• Variable star
  Variable star
  A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
  
  
• Irregular variable
  Irregular variable
  An irregular variable is a type of variable star in which variations in brightness show no regular periodicity. There are two main sub-types of irregular variable: eruptive and pulsating.Eruptive irregular variables are divided into three categories:...
  
  

External links

• Jim Kaler's Stars, University of Illinois: THETA HER (Theta Herculis)
• Spacedude's Constellation map: Stars in Hercules