In the case of the celestial hounds of heaven, the constellations Canis Major and Canis Minor, you can blame Orion the Hunter for turning the doggies loose in our starry skies. The constellation Orion is one of the best known and recognized characters in the night sky. He's certainly the king of the cold winter heavens, surrounded by a gang of bright stars and companion constellations.
According to Greek and Roman mythology, Orion was a nocturnal hermit hunter who was the son of Zeus, the king of the gods. Because of his father's genes, Orion had super-human strength and abilities that gave him a huge advantage over the beasts he hunted.
His only weapon was his mighty club, which he would use to take out the critters he skillfully stalked. Of course, every good hunter has his faithful hunting dogs, and Orion's best friends were his big dog, Canis Major, and his little dog, Canis Minor, which are Latin for big and little dog, respectively. They're also seen as constellations adjacent to the great hunter Orion.
Orion's big dog, Canis Major, is easy to find. From our view it's just to the lower left of Orion, and as you can see, it resembles a dog standing on its hind legs begging for food scraps from its master. The brightest star in the night sky, Sirius, marks the dog's nose. Just use the three stars in a row that outline Orion's belt as a pointer to the lower left, and you'll run right into Sirius.
To the right of Sirius is Mirzam, a dimmer but distinct star that marks the hound's elevated paw. To the lower left of Sirius, you can't help but notice the triangular pattern of stars that outline Canis Major's hind end, hind leg and tail. As Canis Major journeys across the sky from east to west in response to Earth's rotation, the big doggy appears to maintain its begging stance. As a matter of fact, Robert Frost takes note of this in "Canis Major":
The great Overdog
That heavenly beast
With a star in one eye
Gives a leap in the east.
He dances upright
All the way to the west
And never once drops
On his forefeet to rest.
I'm a poor underdog,
But to-night I will bark
With the great Overdog
That romps through the dark.
From "Complete Poems of Robert Frost"
At either end of Canis Major are noteworthy stars. Sirius, at the nose, is not only the brightest star of the constellation but is also the brightest star in the night sky. Sirius is a Greek name that translates to English as "the scorcher." Its brilliance is partially due to its size (it's larger than our sun), but mostly due to its proximity to Earth. Sirius is only eight light-years away, while most other stars we see at a glance are an average of 100 light-years away.
By the way, just one light year equals almost six trillion miles.
At the other end of Canis Major is Aludra, the star at the end of the big dog's tail. It's certainly nowhere near the brilliance of Sirius, but it's one heck of star. It's estimated by astronomers that Aludra is almost a billion miles in diameter, more than ten times the diameter of our sun. The reason it has a reasonably humble appearance in our sky is that it's more than 3,000 light-years away. The light that you see from Aludra tonight left that great star before the year 1.000 B.C.
As majestic as the constellation Canis Major is, Orion's little hunting dog Canis Minor is kind of a joke by comparison, at least in my opinion. It's basically just two stars, Procyon and Gomeisa, and that's it. It's easy to find. Just look for the next brightest star you can see in the sky to the upper left of Sirius. That's Procyon, the brightest star in Canis Minor. Gomeisa is a fainter star to the upper right of Procyon. How those two stars outline a dog is anybody's guess. Maybe it's a wiener dog.
The constellation Orion and his hunting dogs all make contributions to one of the coolest configurations in the sky, the "Winter Triangle." In your mind's eye, draw a line from the bright star Betelgeuse at the armpit of Orion the Hunter to Sirius in Canis Major, and then up to Procyon in Canis Minor. You'll easily see that those three bright stars make up a perfect equilateral triangle from our vantage here on Earth.
Enjoy the hounds of heaven.
(Lynch is an amateur astronomer and author of the book, "Stars, a Month by Month Tour of the Constellations." Contact him at mikewlynch@comcast.net.)