Friday, August 6, 2010
Sirius and the Dog Days of Summer
The Dog Days, the hottest and most sultry days of summer, were named for Sirius, the Dog Star, which rises and sets with the sun during the hottest summer months. Because Sirius was so bright, ancient civilizations believed it added to the heat of the sun causing the more intense heat of July and August. Sirius is the brightest star in the night sky, almost twice as bright as the second brightest star Canopus. Its brilliance is due to its close proximity to Earth and its intense luminosity (25 times brighter than the sun). Although to the naked eye it appears as one star, Sirius is actually a binary star system; Sirius A and the smaller Sirius B orbit around a common point, the star system’s center of mass. Sirius can be found in the constellation Canis Major (Great Dog) often called Orion’s dog.
Many cultures have attached significance to the rising of Sirius. The ancient Egyptians used the rising of Sirius as a “watchdog” to determine the timing of the Nile River’s annual flooding. The ancient Greeks thought Sirius caused dogs to behave abnormally; their increased panting due to the heat was thought to cause disease. The term “star struck” originated when the Greeks decided Sirius was a bad influence on human behavior. Several cultures, including the Romans, offered sacrifices to Sirius in hopes of a good harvest. On the island of Ceos in the Aegean Sea, inhabitants awaited its rising; if Sirius rose clear, it foretold good fortune, but if it was faint or hazy, pestilence was sure to follow.
We can hope Sirius rose clear this year and good fortune (along with cooler weather) is just down the road. The sun is lower in the sky this month than in July, so the sweltering Dog Days will be drawing to a close soon – that’s something, at least.