Canicular Star

Sirius, the brightest star in the night sky, is out of sight now. Thanks to its rising and setting times and our viewing angle, it’s hidden in the Sun’s glare. It’ll return to view in a few weeks.

Thousands of years ago, Sirius first poked into view in the morning sky in early July, when the weather was heating up. Sirius is known as the Dog Star, so the period of the summer’s greatest heat -- when the Dog Star emerged into full view -- came to be known as the Dog Days. The period begins around July 3rd and ends in mid-August.

“Dog Days” is a phrase we still use today, even though Sirius is nowhere in sight. It’s moved because an effect known as precession causes the stars to slide through the seasons.

The Dog Star is also known as Canicula -- a Latin word that means “little dog.” In parts of Mexico, Texas, and other regions, the Dog Days are sometimes called “La Canicula.”

The people of ancient Egypt used several calendars. In one, the new year began with the first appearance of Sirius in the dawn sky. In another, the year was exactly 365 days long -- a quarter of a day shorter than the true year. So the calendar slid out of sync with the Sun by one day every four years. But it came back around once every 1,461 of those years. That span is known as the canicular period -- the time it took the canicular star to return to its rightful place in the calendar, climbing into view in early July.
 

Script by Damond Benningfield