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Dog Days

August 6, 2012

The second-brightest star in the sky is starting to emerge from the glare of the brightest. According to centuries-long tradition, that brings to an end to Dog Days of summer.

Sirius is the brightest star in the night sky. It’s just climbing into view in the morning glow of the brightest star in the daytime sky — the Sun. Sirius is quite low in the east-southeast a little before sunrise. It’s best seen from the southern tier of states, although it’ll pull into better view from the northern states during August.

Sirius is the leading light of the constellation Canis Major, the big dog, so it’s also known as the Dog Star. And that’s where we get the name for this part of summer — the Dog Days.

Sirius makes its closest approach to the Sun during the summer, disappearing for a few weeks in the Sun’s glare. In ancient times, it returned to view in the morning sky by early July — just as the weather was reaching its hottest. It seemed logical that Sirius was the cause — its light and heat added to the Sun's to bring things to a simmer. So the people of ancient Greece and Rome named the period of the year after Sirius returned to view in the morning sky in the star’s honor.

Thanks to an effect known as precession, over the centuries the stars shift position with respect to the Sun. So Sirius now returns to view a few weeks later, with the heat in full force at mid-northern latitudes — the Dog Days of summer.

Script by Damond Benningfield, Copyright 2012


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