The Dog Days of Summer
The Hot Season's Nickname Originates with the Brightest Star Sirius
Jul 14, 2008
It may seem odd that the brightest star in the sky and one associated with the cold nights of winter would be the source of the saying "the Dog Days of Summer," but it is. Sirius is the brightest star in the sky (besides the sun). It is up shining brightly in the night sky during long winter nights and is mostly invisible during the summer due to its closeness to the sun and appearance above the horizon during daylight hours.
Sirius is the alpha star in the constellation Canis Major. Canis Major is called the Big Dog, which gives Sirius its nickname of "the Dog Star". The name Sirius means "scorching," which may relate to its brightness as a star and its relationship to summer. It was because Sirius "disappeared," or joined the sun during the summer, that the saying came about. Ancient Romans believed that Sirius added its warmth to that of the sun's as they neared one another and that this was what produced the hottest days of summer.
When Are the Dog Days of Summer?
The specific days that were traditionally referred to as the Dog Days of Summer were from July 3 to August 11. It was on these days that the Romans saw the Dog Star, Sirius, join the sun at sunrise and disappear from the sky all night. While the Dog Days of Summer are still often considered to be July 3 to August 11, these are no longer the exact dates when Sirius joins the sun in the daytime sky. Because the Earth slowly wobbles on its axis, which is called precession, Sirius does not start rising with the sun in North America until more than a month later, on August 4. So the 40 days following August 4 would be the "new" Dog Days of Summer, ending on September 12.
Precession is also responsible for date changes in another ancient idea: astrology. Just as we still refer to the time period between July 3 and August 11 as the Dog Days of Summer even though the Dog Star does not join the sun for those days, we still refer to people born between July 23 and August 22 as Leos even though the meaning for this is no longer true. The sun is not in the constellation Leo during this time period as it was when the idea of astrology was first devised. Currently the sun enters Leo on August 10 and leaves after September 15. And this time shift is true for all the signs of the Zodiac. Try this quiz to learn more about astrology.
The Dogs of Summer
Many people have incorrectly concluded that the phrase the Dog Days of Summer came about because of an association with actual dogs. Reasons include that these days aren't even fit for a dog or that the heat made dogs go mad.
But it is Sirius the Dog Star in Canis Major that is responsible for the saying. Although you can't observe Canis Major or Canis Minor the Lesser Dog during summer, you can observe other dogs. Canes Venatici, the Hunting Dogs, lie just underneath the handle of the Big Dipper. Learn more about celestial wonders found within these Dogs of Summer.
 |
 |
