Volume 16, Issue 34 - August 21 - August 27, 2008

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Sky Watch by J. Alex Knoll

The Trail of the Dog Star

The Dog Days of summer have passed, but Sirius is just rising

A brilliant star in the east awaits early risers up before the dawn each year at this time. It shines so fiercely that people long ago believed it’s extreme brightness, when rising in conjunction with the sun, resulted in the hottest temperatures of the year, the Dog Days of Summer.

Throughout cultures and the ages, Sirius of the constellation Canis Major, has been associated with a dog. For millennia, the Chinese have seen the star as a heavenly wolf. More than five thousand years ago in ancient Babylon and Mesopotamia, Sirius was the Star of the Dog, the Watch Dog of the Lower Heavens, and images of the star adorned their temples.

During the reign of ancient Egypt, Sirius marked the new year, as its rising with the sun coincided with summer solstice and the annual flooding of the Nile. The star Sirius is linked with the goddess Isis, who rules over the Nile, and the dog-headed god Anubis, keeper of the dead.

Since then, Sirius’ rising has shifted due to the 26,000-year precession of the constellations, caused by Earth’s 231⁄2-degree tilted orbit. Today, Sirius and the sun rise together from July 3 thru August 11, and these are the true, celestial dog days of summer.

The star’s name comes from the ancient Greeks, who dubbed it Sirius, one of Orion’s two hunting dogs, the other Procyon of Canis Minor. Even the word Sirius is hot, derived from the Greek seirius — to sear or scorch.

More than 20 times more luminous than our sun while only twice its mass, Sirius scorches the night sky at magnitude –1.42, twice as bright as any other star. Not only is Sirius the brightest star in the night sky, at 81⁄2 light-years away, it is fifth-closest star to us.


Illustration: © Copyright 1925 M.C. Escher/Cordon Art-Baarn-Holland; Graphics: © Copyright 2007 Pacific Publishers. Reprinted by permission from the Tidelog graphic almanac. Bound copies of the annual Tidelog for Chesapeake Bay are $14.95 ppd. from Pacific Publishers, Box 480, Bolinas, CA 94924. Phone 415-868-2909. Weather affects tides. This information is believed to be reliable but no guarantee of accuracy is made by Bay Weekly or Pacific Publishers. The actual layout of Tidelog differs from that used in Bay Weekly. Tidelog graphics are repositioned to reflect Bay Weekly’s distribution cycle.Tides are based on National Oceanic and Atmospheric Administration and are positioned to coincide with high and low tides of Tidelog.

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