Canis Major

Canis Major (Latin for the greater dog) is one of the 88 modern constellations, and was also in Ptolemy's list of 48 constellations. It is said to represent one of the dogs following Orion the hunter (see also the constellations of Orion, Canis Minor, and Canes Venatici.) Canis Major contains Sirius, the brightest star in the night sky, and that star is part of the Winter Triangle.

Canis Major's alpha star Sirius is the brightest star besides the Sun as seen from Earth. It is also one of the nearest. The star's name means scorching, since the summer heat occurred just after Sirius' heliacal rising. The Ancient Greeks referred to such times in the summer as dog days, as only dogs would be mad enough to go out in the heat, leading to the star being known as the Dog Star. Consequently, the constellation was named after it, as a Big Dog.

Other named stars in Canis Major (all names from Arabic):

• β CMa: Murzim - "The Announcer"
• γ CMa: Muliphen
• δ CMa: Wezen - "The Weight"
• ε CMa: Adhara - "Virgins"
• ζ CMa: Furud - "Bright Single One"
• η CMa: Aludra

There aren't many bright deep sky objects in this region of sky. The only Messier object in Canis Major is M41 (NGC 2287), an open cluster of visual magnitude 4.6. It is located about 4 degrees directly south of Sirius. M41 is roughtly 2350 light years away from Earth, contains about 8,000 stars, and is about 24 light years in diameter. It is also noted for containing a number of K-class stars.

Canis Major Dwarf is a recently-discovered dwarf galaxy orbiting the Milky Way, in the constellation.

This constellation was known to the easterners from the time immemorial. In early European classical days, this constellation represented Laelaps, Actaeon's hound; or sometimes the hound of Procris, Diana's nymph; or the one given by Aurora to Cephalus, so famed for its speed that Zeus elevated it to the sky. Most commonly, Canis Major (or perhaps just the star Sirius) is Orion's hunting dog, pursuing Lepus the hare or helping Orion fight Taurus the Bull, and is referred to in this way by Aratos, Homer and Hesiod. The ancient Greeks refer only to one dog, but by Roman times, Canis Minor appears as Orion's second dog.

Roman myth also refers to Canis Major as Custos Europae, the dog guarding Europa but failing to prevent her abduction by Jupiter in the form of a bull; and as Janitor Lethaeus, the watchdog of Hell.

Depending on the faintness of stars considered, Canis Major resembles a dog facing either above or below the ecliptic. When facing below, since Sirius was considered a dog in its own right, early Greek mythology sometimes considered it to be two headed. As such, together with the area of the sky that is deserted (now considered as the new and extremely faint constellations Camelopardalis and Lynx), and the other features of the area in the Zodiac sign of Gemini (i.e. the Milky Way, and the constellations Gemini, Orion, Auriga, and Canis Minor), this may be the origin of the myth of the cattle of Geryon, which forms one of The Twelve Labours of Herakles.

The stars of the constellation Canis Major can be connected in an alternative way, which graphically shows a dog.

Stars α Canis Majoris, ν Canis Majoris, ο¹ Canis Majoris, ε Canis Majoris, σ Canis Majoris, δ Canis Majoris, and ο² Canis Majoris form the dog's body. Alpha Canis Majoris, also known as Sirius, is of magnitude zero, whereas δ and ε Canis Majoris are of magnitude two, and ο² Canis Majoris is of magnitude three.

The big dog's front right paw is star β Canis Majoris; the dog's front left paw is the star ξ Canis Majoris; the dog's right hind paw is the star ζ Canis Majoris, and the dog's left hind paw is the star κ Canis Majoris. β Canis Majoris is of the second magnitude, whereas ζ Canis Majoris is of the third magnitude.

The big dog's tail consists of stars ω Canis Majoris and η Canis Majoris, with η Canis Majoris being of the second magnitude.

Stars ι Canis Majoris, γ Canis Majoris, and θ Canis Majoris form the dog's head. All three of these stars are of the fourth magnitude.

• H. A. Rey, The Stars — A New Way To See Them. Enlarged World-Wide Edition. Houghton Mifflin, Boston, 1997. ISBN 0-395-24830-2.

Source: The Bright Star Catalogue, 5th Revised Ed., The Hipparcos Catalogue, ESA SP-1200

The astronomer Leslie Peltier had a dog named Canis Major.

Wikimedia Commons has media related to Canis Major.

• The Deep Photographic Guide to the Constellations: Canis Major