WHAT IS THE ‘DOG STAR”

Posted by admin | | Sunday 15 February 2009 8:51 pm

Sirius is the brightest star in the night sky and is known as the “Dog Star”, reflecting its prominence in its constellation, Canis Major.

Sirius the “Dog Star”,  is about twice as massive as our Sun and is 25 times more luminous. — It is also 8.6 light years away, or  5,878,625,373,184  miles.

Orion is very useful as an aid to locating Sirius.  By extending the line of the Belt southeastward, the bright Sirius can be found.

The Voyager 2 spacecraft, launched in 1977 to study distant planets in the Solar System, is now traveling at 3.3 AU per year  (35,034 miles per hour).  At that speed, Voyager 2 is expected to pass Sirius in approximately 296,000 years.

250px-sirius_a_and_b_artwork

Sirius, known in Ancient Egypt as Sopdet, is recorded in the earliest astronomical records. During the era of the Middle Kingdom, Egyptians based their calendar on the helical rising of Sirius, namely the day it becomes visible just before sunrise after moving far enough away from the glare of the sun. This occurred just before the annual flooding of the Nile River and the summer solstice, after a 70 day absence from the skies.

The Ancient Greeks believed that the appearance of Sirius heralded the hot and dry summer, and feared its effects on making plants wilt, men weaken and women become aroused. Due to its brightness, Sirius would have been noted to twinkle more in the unsettled weather conditions of early summer. To Greek observers, this signified certain emanations which caused its malign influence. People suffering its effects were said to be ‘star-struck’.

The season following the star’s appearance came to be known as the Dog Days of summer. The inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes, and would await the reappearance of the star in summer. Coins retrieved from the island from the third century B.C., feature dogs or stars with emanating rays, highlighting Sirius’ importance.

Bright stars were important to the ancient Polynesian for navigation between the many islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations. They also served as latitude markers; the declination of Sirius matches the latitude of the island of Fiji at 17°S and thus passes directly over the island each night.

******************************