Monday, March 2, 2009

The Cross and the Square




Two very prominent shapes in the night sky are the Northern Cross and the Great Square. The first is formed by the five brightest stars forming a cross in the constellation Cygnus (the Swan); the latter is called the Great Square of Pegasus as it is part of the constellation Pegasus.
In Greek mythology Cygnus was the friend of Phaethon, the son of Helius who was the god in charge of carrying the sun across the sky in his chariot each day. When a teenage Phaethon begged his father to let him drive the chariot, Helius relented. On the chosen day Phaethon and Cygnus boarded the chariot and sped recklessly across the sky with the sun in tow. To save the earth from the sun's heat, Zeus, the god of gods, threw a thunderbolt at the chariot causing Phaethon to bethrown from the chariot into a river. Cygnus leapt out of the chariot and saved Phaethon from drowning. To honour Cygnus, Helius turned him into a swan and placed him in the sky.
To find Cygnus (the Northern Cross) follow a line through the two stars on the handle edge of the Big Dipper and as it rises northwest. The Northern Cross is the dominant constellation in this area of the night sky. The best time to view these constellations is between 6 pm and 8 pm, any evening in December. Deneb, the star in the tail of the Swan, is 1600 light years from earth and has 60 000 times the power output of our sun. Albireo, the bright star at the head of the swan is really two stars. When viewed with binoculars the stars appear in two different colours.
To locate Pegasus follow the line from the pointer stars in the Big Dipper through Polaris, the North Star, toward the south. It is twice as far from Polaris to the Great Square as it is from the Big Dipper to Polaris. The Great Square of Pegasus (the winged horse) represents the body of the horse. The four stars in the square are about the width of your fist apart. In the night sky Pegasus is flying upside down. His head and neck are the chain of stars below the Square and his feet are the stars above.
Alpheratz, the star in the upper left hand corner of the Great Square, is one of the stars in the constellation Andromeda. If you search the area on a clear night, it is possible to see the Galaxy Andromeda with the naked eye. It appears as a fuzzy ball.
Before using binoculars, a spotting scope or a telescope, get to know some of the guideposts in the night sky. On a clear night it is possible to see 3000 stars with unaided eyes – enough for anyone starting out. The Big Dipper is the number one guidepost. The two pointer stars on the front edge of the dipper point toward Polaris, the North Star. From this point, with the help of some sky charts, all planets, constellations and galaxies can be located.

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