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, mostly 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 during these cooler October nights, it’s soaring the western sky in the early evening.
Look for the Summer Triangle
The best way to find Aquila is to first look for the Summer Triangle. Just look for the three brightest stars you can see high in the southwestern sky in the early evening and that’s it. 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.
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Altair is on the left-hand point of a large vertical diamond that outlines the wingspan of the 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 to see it. There are no stars in that part of Aquila to help you.
Altair is the 12th brightest star in the sky. And it’s relatively close to Earth — only 97 trillion miles away, which is 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 1 1/2 million miles in diameter, twice as large and 10 times brighter than the sun.
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 at the rate of one full rotation in less than nine hours.
By comparison, the sun takes about a 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.
Through a small to moderate telescope, look for Messier Object 11, just off the tail of Aquila. M 11, as it’s referred to, is technically in a small adjacent constellation called Scutum the Shield. M 11 is a beautiful open cluster of almost 3,000 stars that are more than 6,000 light years away.
These are young stars, only about 220 million years old. To some people, M 11 is known as the Wild Duck Cluster because many people see it as a flock of flying ducks.
The story of Aquila
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The main Greek mythology story about Aquila has the eagle as Zeus’ faithful pet. Zeus 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 of Olympus. Zeus wanted the finest young man he could find to become the bartender of the gods.
He sent Aqulia on a reconnaissance mission where he discovered Ganymede, plucked him up by the shoulders, and delivered him to Zeus. Ganymede proved to be worthy of his forced labor. Zeus rewarded his faithful eagle by placing him among the stars as the constellation we now see high in the southeastern sky.
Incidentally, 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 far the brightest star-like 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.
One of those moons is Ganymede, not only the largest moon of Jupiter but the largest moon in our solar system. It’s even bigger than the planet Mercury.
