Look Up!

Dog days of summer

Mon, 08/08/2016 - 10:30am

When you think of the "dog days of summer," you think of dogs lying around panting in the sun. But in fact this period of extreme heat was named for the Dog Star, Sirius, which rises with the sun during July and August.

As the brightest star in the sky, it has long been observed and tracked by ancient sky-watchers and astronomers. The name "Sirius" derives from the Greek word "Seirios," which literally means "the sparkler" or "the scorcher." In ancient times it was thought that when the two stars rose together, Sirius was adding its heat to that of the Sun, thus creating the northern hemisphere's hottest, driest time of year. Classic writers such as Hesiod and Hippocrates asserted that Sirius had actual power over the weather, attributing summer's heat to this "second sun."

For ancient Egyptians the dawn rising of Sirius was significant because it heralded the annual flooding of the Nile and the consequent renewal of life that kicked off their new year. It was thus revered as the Nile Star. There may have been some connection between Sirius and the god Osiris, who rose from the dead, and his sister/wife, the shining goddess Isis. The Dog Star has also been associated with the dog-headed god of death, Anubis.

For ancient Greeks and Romans the Dog Star was associated with many various dogs of myth, including Cerberus, guardian of the Underworld. But it was most often seen as one of the hunting dogs of Orion. In the night sky (during winter here in Maine) the constellation of Orion the Hunter looms large directly above Sirius and its constellation Canis Major, the Big Dog. Sirius is generally depicted as the dog's nose or eye. Nearby Procyon and its constellation Canis Minor represent the Little Dog. Together the two dogs are chasing Lepus, the starry Rabbit.

Some ancient Chinese astronomers referred to Sirius as the Heavenly Wolf or Celestial Jackal. In an old Indian story, Sirius is Svana, the faithful dog of Prince Yudhistira, who accompanied his master on a quest for the kingdom of heaven. The prince apparently refused to enter heaven's gates if he couldn't bring his dog with him, a sentiment many dog lovers undoubtedly share.

Among the Alaskan Inuit, Sirius is referred to as the Moon Dog, who causes high winds when near the moon. The Pawnee and Osage may have called Sirius the Wolf Star or Coyote Star. The cross-cultural similarities around the world make you wonder if there's something inherently canine about this star.

While the brightest star, with a magnitude of -1.4 (the lower the number, the brighter the star), Sirius is not the closest star to our solar system. That would be Alpha Centauri, a star not visible to us here in the northern hemisphere. Still, at 8.6 light-years away it is among the nearest stars, a mere 50 trillion miles or so away.

During winter months Sirius is easily visible below and slightly to the left of Orion. The easiest way to find it—other than picking out the brightest star in the sky, of course—is to trace a line down through Orion's belt. Sirius, Procyon, and Betelgeuse, the red giant in Orion, form the three points of the Winter Triangle. With a telescope you can also pick out a small white dwarf companion star to Sirius, called the Pup, although this fading star is no youngster by astronomical reckoning.  

Kristen Lindquist is an amateur naturalist and published poet who lives in her hometown of Camden.


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