Canis Major - Constellation of the Month

MYTHOLOGY

Canis Major is positioned in the sky next to Orion and represents the larger of his two hunting dogs. Many see the dog chasing Lepus (The Hare) and aiding Orion in his attempts to capture the mighty bull of Taurus. Canis Major however has its own mythology, linked to Canis Minor, the second hunting dog.

According to some traditions, Canis Major represents a creature named Laelops, a dog so fast that it could catch any prey. Canis Minor on the other hand depicts the Teumessian Fox, an animal that could not be caught.

The fox was terrorizing Thebes and thus Laelops was called upon to rid the city of the menace.

Due to the paradoxical nature of a dog that could catch anything chasing a fox that could not be caught, Zeus finally intervened and turned them both to stone before placing them in the stars for eternity to honour the epic chase.

NOTABLE STARS

Canis Major is home to the brightest star in the sky, Sirius. Sirius means ‘Scorching’ no doubt in reference to its bright appearance in the sky, but also due to it being visible just before sunrise in the middle of summer in the northern hemisphere. Ancient people watched for the ‘heliacal rising’ of certain stars to help them tell the time of year and Sirius’s rising coincided with the hottest days of summer.

It is also known as the ‘Dog Star’ in reference to the hottest days of the year that were known as ‘Dog Days’ This well used phrase also originates from Sirius’s (and Canis Major’s) heliacal rising in June/July.

Despite being the brightest star in the sky, Sirius is not that much bigger than our Sun and thus its brightness is due to its relative proximity to our solar system. At a mere 8.6 light years away, it is one of our closest stars. Canopus, the 2nd brightest star in the sky, is over 300 light years away. If Sirius was the same distance from Earth, it would hardly be noticeable among the multitude of stars in the night sky. If all the stars in Canis Major were viewed from the same distance (‘Absolute Magnitude’), the luminosity of the stars in the constellation would look very different.

DEEP SKY OBJECTS

Canis Major only contains one prominent deep sky object, known as Messier 41. M41 is an open cluster, meaning that all the stars within it were borne from the same dust cloud and are thus related, and travelling through space together.

These young stars will eventually disperse and embark on their own cosmic journeys. The cluster contains over 100 stars and is situated more than 2,000 light years from Earth!

Despite the distance, M41 is visible with the naked eye and binoculars will resolve many of the individual stars. To find M41, simply look a little to the south of Canis Major’s brightest star, Sirius.