As I write this we are riding a string of really hot, really humid, miserable days. These are the dog days of summer, as the saying goes. But did you know that the term “dog day” comes from the realm of astronomy?

And that it has to do with a star that’s not even in the night sky during this time of the year.

Normally the star Sirius is known as a winter/spring star. It is the brightest star in the night sky then. Only over eight light years from earth and monstrously hot to boot, it is one shiny object!

Its name is probably derived from the Greek “seiros,” which means searing. Other peoples gave her similar sounding names. The Celts called her Syr, the Greeks Osiris, and the Egyptians Cahen Sihor.

It’s the Egyptians that have one of the most revered roles for Sirius. But first a little astronomy!

Earth travels around the sun during the year. Our “daytime” is when the side we live on faces the sun. Our “nighttime” is when we are facing away from it. We all learn that in elementary school. But think about that.

Traveling a giant circle all year long means that when we are facing away from the sun - the “center” of our orbit - we are slowly exposing ourselves to new celestial real estate outside our orbit, during the night. The stars we see when we are on this side of the sun are not the stars we see when we are on that side over there months from now, or way over there six months from now.

We see Sirius in our night sky during winter and spring. But where is she now? She is on the daylight side! Unfortunately, the sun brightens the entire sky when it is up so it gets real hard to see the thousands of stars up there during the daytime. But we can cheat a little!

Sirius, being near the sun during this time of the year, will rise with it. The skies are still dark enough during early morning to catch glimpses of stars nearby the sun before full-on daylight kicks in. This phenomenon, when a star rises with the sun, has the fancy title of heliacal rising. And it was of high importance to the Egyptians.

The Nile River meant life to the people of Egypt. And its annual flooding during this time of the year was highly desired because it essentially fertilized all the land around it.

The flooding came about the same time each year, and you’ll never guess what star rose with the sun at that time. Sirius, of course! And Sirius was given the credit for the renewing of the land.

So the annual appearance of Sirius with the sun came with great hope and anticipation. The Egyptians so valued this time of regeneration that they set their calendars by it.

Dr. E. C. Krupp writes in his book Beyond the Blue Horizon, “Egypt, it was said, is a gift of the Nile, but the Nile, as far as the Egyptians were concerned, was a gift of Sirius.”

And the star played other important roles in Egyptian culture, both in their creation myths and in their myths of living and dying and being reborn.

But the Greeks and Romans had a special place for Sirius, as well.

It was in their mythical stories part of the constellation Canis Major, one the dog constellations near Orion. Sirius itself was known as the Dog Star. And it’s here where we finally make the dog connection.

Think of the Mediterranean region during the summer. It’s hot, it’s oppressive. A good time is not had by all. And during the days of the ancients hot, humid weather was not exactly a form of disease control.

And, of course, the hotter weather and all the travail that accompanied it must be due to that searing hot star that rose with the sun - that Dog Star!

Hence, the weeks around which Sirius rises with the sun are the “dies caniculares,” the dog days.

If you are an early riser you can see Sirius rise with the sun. Now understand that rising at the same time as the sun doesn’t necessarily mean at the same place. For us here in southern California, you’ll have to look to the south about 45 degrees, and there she’ll be rising above the horizon just before the sun.

After you take part in this ancient rite of observing the heliacal rising of the Dog Star, start brewing the iced tea, shut the windows, dress lightly, and prepare yourself for what’s likely to be another dog day.