Constellations, otherwise known as groups of stars that allegedly make pictures in the sky, have been dreamed up by humankind throughout the centuries.
Depending on the culture, they can be all kinds of things. Constellations can represent people, monsters, gods, instruments and much more.
In 1922, the International Astronomical Union came up with a standard list of 88 constellations, most from Greek and Roman mythology.
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 at 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 is Vega, in the constellation Lyra the Harp. On the lower left is Deneb, the brightest in Cygnus the Swan. The star on the lower right is Altair, the brightest shiner in Aquila.
As you see in the diagram, Altair is on the lefthand 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 on your imagination — there are no real stars in that part of Aquila.
Altair is the 12th brightest star in the sky, and it’s relatively close, only 16 light-years away. Believe it or not, that’s a lot closer than most stars we see at night.
Because it’s so close, astronomers know quite a bit about it. Altair is almost 1.5 million miles in diameter, twice as large as our sun, but cranking out a lot more light than our home star, more than 10 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 percent larger along its equator than from pole to pole.
Further observations revealed that Altair is rapidly spinning on its axis, one full rotation in under nine hours. By comparison, our sun takes more or less an entire month for one rotation.
Altair, like all stars, is basically a big ball of gas, so its rapid spinning and centrifugal force causes it to bulge at its equator.
Scan your telescope all around Aquila, and you’ll find some nice little 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 3,000 stars.
These stars are about 220 million years old, considered infancy for stellar age.
M11 is called the Wild Duck Cluster, because many people see it as a flock of flying ducks.
The main Greek myth about Aquila has the eagle as Zeus’ 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 shepherd boy, Ganymede, son of King Tros, to become the cup-bearer of the gods on Olympus.
Zeus sent Aqulia to pluck up Ganymede and deliver him to Olympus.
Zeus rewarded his faithful eagle for all his services by placing him among the stars as the constellation we now see high in the southeast sky.
It’s no coincidence that one of the planet Jupiter’s largest moons is named Ganymede, since Jupiter is the Roman name for Zeus.
Jupiter is also easily available in the sky tonight in the low southern skies. It’s by the far the brightest starlike object in that part of the sky. With just a small telescope or even a good pair of binoculars you can see up to four of Jupiter’s moons at one time, looking like little stars on either side of Jupiter’s disk.
Our waxing gibbous moon will be just to the lower left of Jupiter Tuesday evening. That should be a lovely September sight.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and author of the book, “Washington Starwatch,” available at bookstores and at his Web site www.lynchandthestars.com
The Everett Astronomical Society welcomes new members and puts on public star parties. The Web site is members.tripod.com/everett_astronomy.
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