Altair or Alpha Aquilae (Alp Aql) is the brightest naked eye star in the constellation Aquila. With an apparent magnitude of 0.76v, Altair is the 12th brightest star in the entire sky (see: 50 Brightest Stars ). Its absolute magnitude is 2.2 and its distance is 16.8 light years. The Equinox J2000 equatorial coordinates are RA = 19h 50m 47.0s, Dec = +08° 52' 06".

Altair has a spectral type of A7V, a surface temperature of 7500° Kelvin and a luminosity 10.6 times the Sun. It has a mass of 1.79 solar masses and a diameter 1.8 times the Sun.

The image above shows the uncropped view of Altair (North is up) through the Takahashi E-180 Astrograph.

At a distance 16.7 light years (5.13 parsecs), Altair and is one of the closest stars visible to the naked eye. Along with Beta Aquilae and Gamma Aquilae, it forms the well-known line of stars sometimes referred to as the Family of Aquila or Shaft of Aquila. Altair forms one of the vertices of the Summer Triangle along with Deneb and Vega.

Altair is a type-A main sequence star fusing hydrogen into helium in its core. It possesses an extremely rapid rotation rate of 210 kilometers per second at its equator which translates into rotational period of approximately 9 hours. For comparison, the Sun requires just over 25 days for a complete rotation at its equator. This rapid rotation forces Altair to be oblate; its equatorial diameter is over 20 percent greater than its polar diameter.

The description above is based on the Altair entry in Wikipedia. For more information about Altair, see Stars (Jim Kaler).

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