Altair

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Altair-Sun comparison

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Altair PR image6 (white)

Altair

Altair (Alpha Aquilae, α Aquilae, α Aql) is the brightest star in the constellation of Aquila; the Eagle. It is the twelfth brightest star in the night sky, situated at a distance of about 16.7 light-years from Earth. Altair is one of the closest stars visible to the naked eye and is a part of the Summer Triangle in the northern hemisphere, along with Vega and Deneb.

Characteristics

Altair is a spectral type A7V star, indicating it is a white star in the main sequence phase of its life. It has an apparent magnitude of 0.76, making it easily visible to the naked eye under good conditions. Altair is notable for its rapid rotation; it completes a full rotation on its axis approximately every 9 hours. This rapid rotation causes the star to have an oblate shape, with its equatorial diameter being significantly larger than its polar diameter.

The star has a mass about 1.8 times that of the Sun and a radius about 1.7 times as large. Despite its larger size, Altair emits about 11 times more luminosity than the Sun, thanks to its higher surface temperature of approximately 7,500 K.

Observation

Altair, along with Vega and Deneb, forms the Summer Triangle, which is an asterism used by astronomers to navigate the night sky. Altair itself is the southern point of the triangle. The star is best observed during the summer months in the Northern Hemisphere, when it is high in the sky during the evening.

Mythology and Cultural Significance

In many cultures, Altair has been associated with an eagle or bird of prey, reflecting its position in the constellation Aquila. In Chinese astronomy, Altair represents the cowherd in the story of the Cowherd and the Weaver Girl, a tale that is celebrated during the Qixi Festival. The star, along with Vega, symbolizes one of the lovers separated by the Milky Way, only allowed to meet once a year.

Scientific Research

Due to its proximity and brightness, Altair has been the subject of extensive astronomical research. Studies have focused on its rapid rotation and the effects this has on the star's structure and evolution. The use of interferometry has allowed astronomers to measure the oblateness of Altair directly, providing valuable data on the effects of stellar rotation.

In Popular Culture

Altair's name and imagery have been used in various aspects of popular culture, including literature, film, and video games. It often symbolizes swiftness and agility, traits attributed to the celestial eagle.

See Also

• List of brightest stars
• Spectral classification
• Main sequence star
• Asterism (astronomy)