Canis Major

History

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

Alpha Canis Major, Sirius ( 6h 45m - 16° 43') has a magnitude of -1.5 and with a distance of 8.6 light years, is the second brightest star in the sky. Sirius is a blue-white class AI star with a surfce temperature of about 10,200 K. It is part of a binary system having a white dwarf companion of magnitude 8.5 is known both as Sirius B and the Pup. Sirius B was the first example found of a white dwarf. Sirius transits on February 16.

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.