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AQUILA
The Eagle
Aquila - Celestial Atlas by Alexander Jamieson - 1822
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Aquila, the eagle, is another very ancient constellation, known as an eagle well before the birth of Christ. In Greek mythology, Aquila was an eagle attendant to Zeus (Jupiter), king of the gods, and performed deeds in his service. The most notable of these were the retrieval of the god's thunderbolts, and the fetching of the beautiful Trojan boy, Ganymede, up to the heavens to be the catamite of Zeus, and the cup bearer of the gods. Ganymede is represented by the nearby constellation Aquarius, and Aquila is seen swooping down towards him, just as the ancient stories tell. The abduction of Ganymede by the eagle Aquila has been portrayed by a long list of classical artists, including Michelangelo, Rembrandt, and Rubens. (The above image from Jamieson's Celestial Atlas contains two constellations, Antinous, and Taurus Poniatowski, that are now obsolete, not included in the 1930 formalization of the constellations by the International Astronomical Union.)
The alpha star in Aquila is Altair, Arabic for the flying eagle.It is the twelfth brightest star in the sky, with a magnitude 0.77, and itt is one of the closest stars to Earth, only 16 light years away. It is also unique in that it is one of the fastest rotating stars known. Our Sun completes one rotation every 25.4 days, whereas Altair, which is half again as large as our Sun, completes one rotation in only 6.5 hours. This rapid rotation would cause the star to be significantly flattened at the poles, giving it an ellipsoid shape, rather than the normal sphere.
Beta Aquilae is named Alschain, another Arabic term for eagle or falcon. It is 40 light years away, with a magnitude of 3.71.
Gamma Aquila is named Tarazed, an ancient Persian name. It is over 300 light years away, with a magnitude of 2.67.
Zeta Aquilae is named Deneb El Okab, Arabic for tail of the eagle. It is 83 light years away, with a magnitude of 2.98.
Located as it is, in the middle of the Milky Way, Aquila has lots to offer the observer. There are star clusters like NGC 6709, and dark nebulae, like B143, and two planetary nebulae (shown below) that have nothing to do with planets. So named because their shape resembles the disk of a planet through a small telescope, they are actually shells of expanding gas from dying stars.
With an apparent magnitude of only 11.9, NGC 6751 is barely discernible in a small scope, but through the eyes of the Hubble Space Telescope, it is a wondrous sight indeed. The nebula is almost a light year in diameter, 600 times larger than our entire solar system. The gas is illuminated by the intense radiation of the exposed core of the dying star at its center. NGC 6751 is 6,500 light year away.
NGC 6781 is also a faint nebula, with an apparent magnitude of 11.8.
There have been six stars found so far in Aquila that have planets orbiting them. One of these stars has a magnitude of 4.72, and is easily visible to the naked eye. It is catalogued as 49 Aql (or Ksi Aql), and sits right beside the bright Altair. The star is 203 light years away, with a planet almost three times the size of Jupiter. For more information on exoplanets, visit NASA's Planet Quest.
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