The hottest, muggiest days of the year are in July and August and are often referred to as the "dog days of summer."
You may imagine an old dog spread out snoozing under a shade tree on a summer afternoon. But "dog days" is an ancient term with an astronomical origin.
The Romans called the hot days of summer caniculares dies (dog days in Latin). Sirius, the "Dog Star," is the brightest star in the sky and is in Canis Major, the Great Dog.
In ancient times, Sirius rose on hot summer mornings just before the sun. Due to the slow spin of the Earth on its axis over a 26,000-year period known as the precession of the equinoxes, Sirius now rises later in the summer than in ancient times. However, it still retains its link to hot summer days of August.
The sun rises Friday at 5:41. If you look southeast at 5:30 and scan the horizon with binoculars, you should be able to see Sirius hovering just 6 degrees above the horizon. Sirius is quite bright, but its low position on the horizon and the brightening twilight will make it a challenge.
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Sirius and Canis Major will become easier to view in the pre-dawn sky, becoming fairly easy to see by the end of the month.
While you're at it, look for Orion higher above the horizon than Sirius, and bright Jupiter even higher above the horizon.
If you're lucky enough to find Sirius Friday or in the next several weeks on a muggy morning, you can appreciate why the Romans felt Sirius was the cause of hot, sultry weather. It's somewhat ironic that we now consider Sirius one of our winter stars, because we are used to seeing it best in all its blazing glory on cold winter evenings after sunset.
If you go
Learn more about the summer night sky at a free astronomy event. Friday's meeting of the Tucson Amateur Astronomy Association features a lecture on "Mapping the Heavens" by Ken Graun, who has written beginning-astronomy books and star charts for children and adults. TAAA member Mary Turner will also explain the summer night sky, constellations, folklore and how to find objects within them. The free event starts at 6:30 p.m. at the Steward Observatory lecture hall, 933 N. Cherry Ave.
Contact Tim Hunter at skyspy@azstarnet.com