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The constellation of the Great Dog, usually known by its Latin name Canis Major, is the one constellation whose shape is not needed for identification. It is dominated by Sirius or alpha Canis Major, the brightest star in the sky with an apparent magnitude of –1.4. Sirius is a white star and only 8.7 light-years from the Earth. It has a small companion that can only be seen through a large telescope. Sirius will appear over the horizon about half an hour after the constellation Orion has risen.
The ancient Egyptians were found of Sirius and at times worshipped it. The appearance of Sirius provided a warning that the Nile River was about to overflow its banks. In other words, Sirius was not only a dog, but a watchdog providing a warning of the most important annual event in ancient Egypt. Sirius is known as the Dog Star to this day. While according to the Greeks, the god Zeus placed Sirius in the sky as a reward for its swiftness, sometimes Sirius is referred to as Orion’s dog because of the nearby constellation of Orion.
Sirius forms the most southerly point of a giant hexagon that dominates the winter sky and is considerably larger than the Summer Triangle. The other apexes of the hexagon starting from Sirius and going clockwise are Procyon of the constellation Canis Minor (the Little Dog), Pollus of Gemini the Twin, Capella of Auriga, Aldebran of Taurus and finally Rigel of Orion. The band of the Milky Way runs straight through the middle of the hexagon.