Beta Herculis (Beta Her, β Herculis, β Her), which has the traditional name Kornephoros, is the brightest star in the northern constellation of Hercules at a base apparent visual magnitude of 2.81. This is a suspected variable star with an apparent magnitude that may rise as high as 2.76. Based upon parallax measurements, it is located at a distance of 139 light-years (43 parsecs) from Earth.
Although β Herculis appears to the naked eye to be a single star, in July 1899 the American astronomer W. W. Campbell discovered from spectroscopic measurements that its radial velocity varies, and concluded that it is a binary system. An orbit for the binary was computed in 1908 based upon additional spectroscopic measurements.
At Palomar Observatory, Antoine Labeyrie and others used speckle interferometry with the Hale Telescope to resolve the system in 1977. The Hipparcos satellite observed the orbital motion of the primary relative to other stars, and an orbit was computed in 2005 using spectroscopic data together with these measurements. The period of the system is around 410 days. They have a high orbital eccentricity of 0.55 and the orbital plane is inclined 53.8° to the line of sight from the Earth.
The primary star in this binary system has a stellar classification of G7 IIIa, indicating that it is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. It has a mass nearly three times the mass of the Sun, and has expanded to 17 times the Sun's radius. The effective temperature of the star's outer envelope is about 4,887 K, which gives it the yellow hue of a G-type star. The secondary star has a mass only 90% that of the Sun.
Naming and etymology
According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, al-Nasaq al-Sha'āmī or Nasak Shamiya were the title for three stars :β Ser as Nasak Shamiya I, γ Ser as Nasak Shamiya II, γ Her as Nasak Shamiya III (exclude this star)
In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, δ Serpentis, α Serpentis, ε Serpentis, δ Ophiuchi, ε Ophiuchi and ζ Ophiuchi. Consequently, β Herculis itself is known as 天市右垣一 (Tiān Shì Zuǒ Yòu yī, English: the First Star of Right Wall of Heavenly Market Enclosure), represent Hézhōng (河中), possibly Hezhong Municipality or Hezhong Circuit (see : Wang Chongrong, formally the Prince of Langye 瑯琊王, was a warlord of the late Chinese dynasty Tang Dynasty who controlled Hezhong Circuit, headquartered in modern Yuncheng, Shanxi). Hézhōng (河中) was westernized into Ho Chung by R.H. Allen, which means "in the river".
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