The constellation Canis Major, the greater dog has been known since ancient times as the dog of Orion. The brightest star, Sirius however, has been far more prevalent in history. Sirius was important to the Egyptians because its appearance in the east foretold the rising of the river Nile. Many temples were built in its honor, including the Temple of Isis at Denderah. Sirius is called the dog star, and the term dog days comes from references to this star. Because this star was so bright, it was believed it was also close. This led to the conclusion that when Sirius rose heliacally with the Sun, the two together would cause hotter weather. Thus, the dog days.
For the Observer
Autumn and Winter Skies
M41 ( 6h 44m.9 -20° 42') is a loose open cluster about 4 degrees south of Sirius. The cluster is about 2400 light years distant with a diameter of roughly 20 light years. At the center of this cluster is a star that is remarkably red. It has a magnitude of 6.9 and is class K3.
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Kathy Miles, Author, and Chuck Peters, Systems Administrator