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Following faithfully at Orion's heels is Canis Major, the big dog. It is the constellation containing the brightest star in the night sky: Sirius, the Dog Star. Being the brightest star in the sky, Sirius has naturally had a lot of attention from cultures all over the world throughout history, and the recurring theme of canine associations speaks to the common origins of all things human.
In ancient Egypt, Sirius was revered as the Nile Star, or the Star of Isis. Throughout the winter and spring, Sirius rises four minutes earlier each night (as all stars do), until by the summer solstice (June 22) it is rising just before dawn. Some Egyptian temples (and Mayan temples as well) were aligned with window openings facing east directly where the Dog Star rose, and when the light from the star shone through the opening, it meant the Nile was about to commence its annual flood, spreading its waters and rich soil over the adjoining floodplain , an occurrence critical to the survival of the Egyptian people.
By the time the hot days of July and August arrive, Sirius is rising with the Sun, beginning the dog days of summer. In ancient times Sirius was blamed, in the words of Robert Burnham Jr., for "bringing forth fever in men and madness in dogs." Dante spoke of "the great scourge of days canicular". Virgil wrote, "the Dog Star, that burning constellation, when he brings drought and diseases on sickly mortals, rises and saddens the sky with inauspicious light". Even in Homer's Illiad, we read of the wrathful Achilles "blazing as the star that cometh forth at Harvest-time, shining forth amid the host of stars in the darkness of the night, the star whose name men call Orion's Dog. Brightest of all is he, yet for an evil sign is he set, and bringeth much fever upon hapless men..."
The name Sirius is Greek for scorching. It is an A1 main sequence star, 1.8 times the diameter of the Sun. The reason it is so bright is because it is so close, only 8.7 light years away, the fifth closest star to Earth. From the northern hemisphere, Sirius appears low in the southern sky, and like all bright celestial objects close to the horizon, atmospheric refraction gives it a decidedly sparkling, or twinkling appearance.
Although Sirius is unmistakably blue/white in colour, nearly all ancient texts refer to it as red. Some suggest that colours were sometimes interpreted differently in ancient times. But another possible explanation surfaced with the 1862 discovery of a tiny companion star to Sirius, named Sirius B, or the Pup. It is a white dwarf star, and a white dwarf is the evolutionary descendent of a red giant, leading to the speculation that in ancient times it was in fact a red giant that overshadowed Sirius, accounting for the red colour. Although this seems to contradict the accepted theory that it takes at least 100,000 years for a red giant to become a white dwarf, it is still a very real possibility. Below is the first photo of Sirius B, by Irving Lindenblad, 1973.
The Dogon tribe of Mali, Africa, have tribal traditions that include the knowledge of Sirius B, the tiny companion star that is impossible to see without the largest of telescopes. They also know that it orbits Sirius every 50 years, and that it is extremely dense, and heavy. They also possess the knowledge of many other astronomical facts completely inconsistent with a primitive tribe in the darkest jungles of Africa. There is no record of early missionaries visiting them and imparting them with this knowledge, although the possibility cannot be ruled out. The popular and more exciting (albeit fanciful) theory is that sometime in their past the Dogon tribe acquired this information when they were paid a visit by extraterrestrials...
Just below Sirius is the bright open star cluster M41, visible to the naked eye, and a favourite object for backyard telescopes. Click on photo for larger image.
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