The Little Dog

¡SkyCaramba! Weekly astronomy blog for the week ending January 26, 2013

You’ve probably heard of Canis Major, the big dog. Surely, you’ve seen its bright star Sirius. There’s also a little dog, Canis Minor. Its bright star is Procyon. It’s just 11 light years from us.

Procyon is Greek for “before the dog”. In northern latitudes, Procyon rises before Sirius. That explains the name, although it doesn’t rise much earlier. Thousands of years ago, the stars’ positions were a little different and Procyon was distinctly earlier. You’ll see Procyon to the left of Sirius when both are already up and rising in the east.

Like Sirius, Procyon is actually two stars. Also like Sirius, astronomers knew of the second star long before they could see it. Careful measurements of Procyon A’s position in 1844 revealed it to wobble. They knew another star was tugging on it gravitationally. Astronomers discovered Procyon B in 1896. They orbit each other in 40 years.

In ancient Egypt, seeing Procyon rising in the dawn was a sign of a season. The Nile River would soon flood. Since the civilization depended on the river, many of its people lived close to it. But they had to leave their homes once a year when the water rose. This bright star was like a mark on the calendar reminding them the flooding season would come soon.

The next brightest star in Canis Minor is Gomeisa. The National Audubon Society Field Guide to the Night Sky says the full Arabic meaning is “the little bleary eyed one with filth in the corner of the eye”. Most astronomy writers shorten the translation to “the little bleary eyed one”. In any case, no one knows why the star is so named. Let us hope that in our lifetimes someone unearths an ancient parchment bearing a long forgotten and most intriguing tale to explain it.

Procyon is one of three stars in the “winter triangle”. Sirius is one of the others. Betelgeuse is the third.