Constellations, otherwise known as groups of stars that allegedly make pictures in the sky, have been dreamed up by humankind throughout the centuries and depending on the culture, they can be all kinds of things. Constellations can represent people, monsters, gods, instruments and much more. Back in 1922, the International Astronomical Union came up with a standard list of 88 constellations, most from Greek and Roman mythology tales. Eight of these constellations are birds. Aquila the Eagle is one of the best of the bird constellations, and in the month of September it's flying high in the southeastern sky.
The best way to find Aquila is to use the handy tool known as the "Summer Triangle". Just look for the three brightest stars you can see high in the southeast sky in the early evening this time of year and that's it, the big triangle. Each of these stars is the brightest in their own three respective constellations. The highest and brightest star is Vega, the brightest star in the constellation Lyra the Harp. On the lower left is Deneb, the brightest star in the Cygnus the Swan. The star on the lower right of the Summer Triangle is Altair, the brightest shiner in Aquila the Eagle.
As you see on the diagram, Altair is on the left hand point of a large vertical diamond that without too much imagination outlines the wingspan of the heavenly eagle. Altair is at the heart of the eagle. To the right of the star on the right side of the diamond, you'll see a faint line of stars that outline the tail of Aquila. The head of the eagle is on the left side of Altair, but you'll have to rely totally on your imagination to see it. There are no real stars in that part of Aquila to help you.
Altair is the 12th brightest star in the sky and it's relatively close, only 16 light years or about 97 trillion miles away. Believe it or not, that's a lot closer than most stars we see in the night sky. Because it's so close astronomers know quite a bit about it. Altair is almost one and a half million miles in diameter, twice as large as our sun but cranking out a lot more light than our home star, more than ten times as much.
The most fascinating discovery made about Altair is that it has a bulging waistline. The Palomar observatory in California discovered that Altair's diameter is more than 20% larger along its equator than from pole to pole. Further observations revealed that Altair is rapidly spinning on its axis at the rate of one full rotation in less than 9 hours. By comparison our sun takes more or less an entire month for one rotation. Altair, like all other stars, is basically a big ball of gas, so it's rapid spinning and centrifugal force, the same force you feel on a fast merry go round, causes Altair to bulge out at its equator something fierce.
Scan your telescope all around Aquila and you'll find some nice little star clusters of young stars, but the best eye candy through a small to moderate telescope is Messier object 11, just off the tail of Aquila. Actually M11, as it's referred to, is technically in a small adjacent constellation called Scutum the Shield. M11 is a beautiful open cluster of almost 3000 stars more than 6000 light years, or 35 thousand trillion miles away! These are young stars only about 220 million years old, which is considered infancy for stellar age. M11 has a nickname, the "Wild Duck Cluster", because many people see it as a flock of flying ducks. Crank up your imagination to see that image!
The main Greek mythology story about Aquila has the eagle as Zeus's faithful pet. Zeus, of course, was the king of the gods of Mount Olympus. Aquila accomplished many missions for Zeus, including torturing enemies and delivering thunderbolts. The eagle's main claim to fame was his capture of the Trojan shepard boy, Zeus!
Diagram of the AUILA...Click