'Altair' (α Aql / α Aquilae /
Alpha Aquilae / Atair ) is the brightest
star in the
constellation Aquila and the
twelfth brightest star in the nighttime sky, at
visual magnitude 0.77.
Altair is a
vertex of the
Summer Triangle. It is an "A" type or
white star located 17
light years away from Earth (about 159 trillion kilometers or 100 trillion miles), one of the closest stars visible to the
naked eye.
The name "Altaïr" is
Arabic for "the Flying", from the phrase 'نسر الطائر' ''an-nasr aţ-ţā?ir'' "the Flying Eagle".
The spelling "Atair" is also used frequently.
It is officially known as 河鼓二 (Hégǔ'èr, the Second Star of the Drum at the River, or more literally, Riverdrum II) in Chinese. However, it is more famous known as its other names: 牵牛星 or 牛郎星 (the Star of the Cowherd), after the Cowherd in the Chinese mythology: the
Cowherd and the Weaver Girl.
Altair is most notable for its extremely rapid rotation; by measuring the width of its
spectral lines, it was determined that its
equator does a complete rotation in about 6½ hours (various other sources give 9 hours, or 10.4 hours). For comparison, our Sun requires just over 25 days for a complete rotation. As a result of its rapid rotation, Altair is
oblate: its equatorial diameter is at least 22 percent greater than its polar diameter. Recently, images of the surface of Altair have been captured. This is the first visual verification of
gravity darkening.
Altair, along with
Beta Aquilae and
Gamma Aquilae, form the well-known line of stars sometimes referred to as the shaft of Aquila.
Location
The star's location in the constellation of Aquila is shown in the following map:
Altair in mythology and culture
In
Chinese mythology, there is a love story of
Qi Xi in which Niu Lang ('Altair') and his two children (Aquila -β and -γ) are separated forever from their mother Zhi Nü (
Vega) who is on the far side of the river, the
Milky Way. The Japanese
Tanabata festival is also based on this legend.
In
astrology, the star Altair was ill-omened, portending danger from
reptiles.
See also
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Altair in fiction
External links
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Report on ultra high-resolution photograph.
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SolStation
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Secrets of Sun-like star probed
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