Omega Herculis (ω Herculis, abbreviated Ome Her, ω Her) is a binary star system in the northern constellation of

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 ...

. Based upon an annual parallax shift of 13.04 mas as seen from Earth, it is located around 250 light-years from 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 infrared radi ...

. It is faintly visible to the naked eye, having a combined

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 4.58. The system is a candidate for membership in the Ursa Major Moving Group, although this remains uncertain. The two components are designated Omega Herculis A (officially named Cujam , the traditional name of the system) and B.

Nomenclature

''ω Herculis'' ( Latinised to ''Omega Herculis'') is the system's Bayer designation. It previously bore the

Flamsteed designation A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England. They are named for John Flamsteed who first used them while co ...

of ''51 Serpentis'' before being added to Hercules. The designations of the two components as ''Omega Herculis A'' and ''B'' derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

(IAU). The system bore the traditional name ''Cujam'' (also written as ''Cajam'' and ''Kajam''), meaning ("club"). In 2016, the

organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name ''Cujam'' for the component Omega Herculis A on February 1, 2017 and it is now so included in the List of IAU-approved Star Names. 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 ...

, (), meaning '' Dipper for Liquid'', refers to an asterism consisting of Omega Herculis, ''49 Serpentis'', ''13 Herculis'', 29 Herculis and ''33 Herculis''. 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 ofte ...

for Omega Herculis itself is (, en, the First Star of Dipper for Liquid).香港太空館 - 研究資源 - 亮星中英對照表
, Hong Kong Space Museum. Accessed on line November 23, 2010.

Properties

The primary, Omega Herculis A, is a chemically peculiar

Ap star Ap and Bp stars are chemically peculiar stars (hence the "p") of spectral types A and B which show overabundances of some metals, such as strontium, chromium and europium. In addition, larger overabundances are often seen in praseodymium and neo ...

with a stellar classification of A2 Vp CrSr. 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 colors ...

displays abnormally strong absorption lines of chromium and strontium, and weak lines of calcium and magnesium. An

A-type star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

, it has an estimated 2.14 times the mass of the Sun and 3.30 times the Sun's radius. The star is around 149 million years old and is radiating 70 times the

solar luminosity The solar luminosity (), is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal ...

from its photosphere at an effective temperature of 10,052 K. This component is an Alpha² Canum Venaticorum variable with a brightness amplitude of 0.4 magnitude and a 2.951 day phase that presumably matches the rotation period. The pattern of variation shows that there are regions of the star's surface where the concentrations of elements differ. The star also displays short period variations on the order of 2.5 hours. It has a mean effective magnetic field value of . The secondary, Omega Herculis B, is a magnitude 11.5 companion star. As of 2010, it was located at an angular separation of 0.80

arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The n ...

s along a

position angle In astronomy, position angle (usually abbreviated PA) is the convention for measuring angles on the sky. The International Astronomical Union defines it as the angle measured relative to the north celestial pole (NCP), turning positive into the ...

of 294°.

References

{{DEFAULTSORT:Omega Herculis A-type main-sequence stars Ap stars Binary stars Ursa Major Moving Group Hercules (constellation) Herculis, Omega Cujam Durchmusterung objects Herculis, 024 148112 080463 6117