Altair

Altair is the brightest star in the constellation Aquila and the 12th brightest in the night sky at magnitude 0.77. It is a white main-sequence star of spectral type A7V, only 16.7 light-years from Earth. Altair rotates extremely rapidly — once every 8.9 hours — causing it to be noticeably oblate, with its equatorial diameter about 22% larger than its polar diameter. It is about 1.8 times the mass of the Sun and roughly 11 times more luminous.

Altair is one of the three vertices of the Summer Triangle, along with Vega and Deneb. It is flanked by two dimmer stars — Tarazed (Gamma Aquilae, magnitude 2.7) to the northwest and Alshain (Beta Aquilae, magnitude 3.7) to the southeast — creating a distinctive compact line. Altair is visible from virtually all inhabited latitudes. Best observed from June through November when the Summer Triangle dominates the evening sky.

The name Altair comes from the Arabic 'al-Nasr al-Ta'ir' meaning 'the flying eagle.' In Chinese and Japanese mythology, Altair represents the Cowherd (Niulang/Hikoboshi), separated from the Weaver Girl (Vega) by the celestial river of the Milky Way, reunited once a year on the seventh day of the seventh month — celebrated as the Qixi/Tanabata festival. Altair's rapid rotation and oblateness were directly confirmed by interferometric imaging in 2007.