Vega
Vega（ ['vi:gə] 织女星） is the brightest star in the constellation Lyra（天琴座）, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus( [ɑ:k'tjuərəs] 大角星). It is a relatively nearby star at only 25 light-years from Earth, and, together with Arcturus and Sirius（['siriəs] 天狼星）, one of the most luminous stars in the Sun's neighborhood.
Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Historically, Vega served as the northern pole star around 12,000 BCE and will do so again at 13,727 CE when the declination will be +86°14'. Vega was the first star other than the Sun, to have its photograph taken and the first to have its spectrum photographed. It was also one of the first stars to have its distance estimated through parallax（ ['pærəˌlæks] 视差） measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system.
In terms of years, Vega is only about a tenth the age of the Sun, but it is evolving so quickly that it has already approached the midpoint of its life expectancy, as has the Sun.
Each night the positions of the stars appear to change as the Earth rotates. However, when a star is located along the Earth's axis of rotation, it will remain in the same position and thus is called a pole star. The direction of the Earth's axis of rotation gradually changes over time in a process known as the precession of the equinoxes（岁差）. A complete precession cycle requires 25,770 years, during which time the pole of the Earth's rotation follows a circular path across the celestial sphere that passes near several prominent stars. At present the pole star is Polaris, but around 12,000 BCE the pole was pointed only five degrees away from Vega. Through precession, the pole will again pass near Vega around 14,000 CE. It is the brightest of the successive northern pole stars.
In Chinese mythology, there is a love story of Qi Xi 七夕 in which Niu Lang 牛郎 (Altair) and his two children (β and γ Aquilae) are separated from their mother Zhi Nü 織女 (Vega) who is on the far side of the river, the Milky Way 銀河. However, one day per year on the seventh day of the seventh month of the Chinese lunisolar calendar, magpies make a bridge so that Niu Lang and Zhi Nü can be together again for a brief encounter. The Japanese Tanabata festival, in which Vega is known as Orihime (織姫), is also based on this legend.
Medieval astrologers counted Vega as one of the Behenian stars and related it to chrysolite（['krisəlait]橄榄石）and winter savory(冬香薄荷). Cornelius Agrippa listed its kabbalistic（[ˌkæbə'listik]adj. 卡巴拉的） sign under Vultur cadens, a literal Latin translation of the Arabic name. Medieval star charts also listed the alternate names Waghi, Vagieh and Veka for this star.
Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Historically, Vega served as the northern pole star around 12,000 BCE and will do so again at 13,727 CE when the declination will be +86°14'. Vega was the first star other than the Sun, to have its photograph taken and the first to have its spectrum photographed. It was also one of the first stars to have its distance estimated through parallax（ ['pærəˌlæks] 视差） measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system.
In terms of years, Vega is only about a tenth the age of the Sun, but it is evolving so quickly that it has already approached the midpoint of its life expectancy, as has the Sun.
Each night the positions of the stars appear to change as the Earth rotates. However, when a star is located along the Earth's axis of rotation, it will remain in the same position and thus is called a pole star. The direction of the Earth's axis of rotation gradually changes over time in a process known as the precession of the equinoxes（岁差）. A complete precession cycle requires 25,770 years, during which time the pole of the Earth's rotation follows a circular path across the celestial sphere that passes near several prominent stars. At present the pole star is Polaris, but around 12,000 BCE the pole was pointed only five degrees away from Vega. Through precession, the pole will again pass near Vega around 14,000 CE. It is the brightest of the successive northern pole stars.
In Chinese mythology, there is a love story of Qi Xi 七夕 in which Niu Lang 牛郎 (Altair) and his two children (β and γ Aquilae) are separated from their mother Zhi Nü 織女 (Vega) who is on the far side of the river, the Milky Way 銀河. However, one day per year on the seventh day of the seventh month of the Chinese lunisolar calendar, magpies make a bridge so that Niu Lang and Zhi Nü can be together again for a brief encounter. The Japanese Tanabata festival, in which Vega is known as Orihime (織姫), is also based on this legend.
Medieval astrologers counted Vega as one of the Behenian stars and related it to chrysolite（['krisəlait]橄榄石）and winter savory(冬香薄荷). Cornelius Agrippa listed its kabbalistic（[ˌkæbə'listik]adj. 卡巴拉的） sign under Vultur cadens, a literal Latin translation of the Arabic name. Medieval star charts also listed the alternate names Waghi, Vagieh and Veka for this star.
