Leading the Dog

Two “dog stars” hunker low in the east and southeast as night falls about now, and scamper higher across the sky later on. One of them rises a bit earlier than the other — a fact reflected in its name: Procyon means “before the dog.”

Procyon is the brightest star of Canis Minor, the little dog. It rises a few minutes earlier than Sirius, the brightest star in all the night sky. Sirius is also the leading light of Canis Major, the big dog, so it’s known as the Dog Star.

Because of their relative locations in the sky, Procyon always rises before Sirius — but only from north of roughly 30 degrees north latitude. Below that line, Sirius rises first.

Although Procyon isn’t as bright as Sirius, it’s still one of the most prominent stars in the night sky. In fact, the two stars look so bright for the same reasons — they are fairly bright, but more important, they’re both close neighbors.

Sirius is about 26 times brighter than the Sun, but it’s also less than nine light-years away — closer than only a few other star systems. Procyon is only about a third as bright as Sirius, and it’s about three light-years farther, so it looks a good bit fainter as it leads the Dog Star across the night sky.

The two stars are quite low as the sky gets good and dark tonight. Procyon stands due east, with Sirius well to its right, posing a little lower in the sky as seen from most of the United States.

Tomorrow: subtle color for a big planet.

Script by Damond Benningfield