The constellations Canis Major and Canis Minor are Orion the Hunterís faithful companions in our starry skies. Orion is one of the best known and most recognized characters in the night sky. Heís undoubtedly the king of the cold winter heavens, surrounded by a gang of bright stars and companion constellations like the hounds of winter. Get a good look at them now in the low western sky after sunset because a month or so from now theyíll already be below the western horizon in the early evening.
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 fatherís genes, Orion had superhuman strength and abilities that gave him a massive advantage over the beasts he hunted down. 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 Orionís best friends were his big dog, Canis Major, and his little dog, Canis Minor, which are Latin for big and little dog respectively. Theyíre also seen as constellations adjacent to the great hunter Orion.
Orionís big dog, Canis Major, is easy to find. From our view itís just to the left of Orion, and as you can see it really resembles a dog. The brightest star in the night sky, Sirius, marks the dogís nose. Just use the three stars in a row that outline Orionís belt as a pointer to the left, and youíll run right into Sirius. To the lower right of Sirius is Mirzam, a dimmer but distinct star that marks the houndís elevated paw. To the lower left of Sirius you canít help but notice the triangular pattern of stars that outlines Canis Majorís hind end, hind leg, and tail. As Canis Major journeys across the sky from east to west in response to Earthís rotation, the big doggy appears to be begging from his master.
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. Its brilliance is partially because itís a star larger than our sun, but it is mostly because itís so much closer to us than most other stars. Itís only 8 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 dogís tail. Itís certainly nowhere near the brilliance of Sirius, but itís one heck of a star! Astronomers estimate that Aludra is almost a billion miles in diameter, over ten times the diameter of our sun. The reason it has a reasonably humble appearance in our sky is that itís over 3000 light-years away! The light that you see from Aludra tonight left that great star before the year 1000 B.C!
As majestic as the constellation Canis Major is, Orionís little hunting dog Canis Minor is kind of a joke by comparison, at least in my opinion. Itís basically just two stars, Procyon and Gomeisa, and thatís it. Itís easy to find. Just look for the next brightest star you can see directly above Sirius. Thatís Procyon, the brightest star in Canis Minor. Gomeisa is a fainter star just to the upper right of Procyon. How those two stars outline a dog is anybodyís guess. Maybe itís a wiener dog!
The constellation Orion and his hunting dogs all make contributions to one of the coolest configurations in the sky, the ďWinter TriangleĒ. In your mindís 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. Youíll quickly see that those three bright stars make up a perfect equilateral triangle from our vantage here on Earth.
Enjoy the hounds of heaven before they go into summer hiding!
Diagram of CANIS MAJOR AND MINOR...Click