Dog lovers may wonder what dogs have to do with the hottest days of the year: the dog days of July and August. Actually, the inspiration for the term “dog days” is not some hapless hound but a star: Sirius, the dog star. Sirius is called the dog star because it is the brightest star in the constellation Canis Major (the name in English means “Big Dog”).
In ancient Egypt and in Rome, Sirius rose in the east on summer mornings just before the sun. People understood astronomy well enough to know that Sirius and the sun would travel together all day long, and imagined that the combined power of the bright dog star and the sun was the cause of hot weather. As we know, Sirius like other stars is not visible during the day because its glow is overpowered by Earth’s sunlit atmosphere.
People had mixed feelings about the dog star. In Egypt, farmers looked for the arrival of Sirius to predict the yearly flooding of the Nile, which they needed in order to raise crops. But in Rome, Sirius was disliked because it threatened to bring drought as well as heat. The poet Virgil complained:
Parched was the grass, and blighted was the corn:
Nor escape the beasts; for Sirius from on high,
With pestilential heat infects the sky.
Each year the Romans sacrificed a dog to Sirius in hope the star would grant them a reprieve from hot weather. In the summers of today’s world, Sirius is not visible until about the second week of August. Its constellation, Canis Major, travels with Orion and is best seen during nights from mid winter to early spring.

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