Canis Major is a constellation in the southern hemisphere. Its name means "the greater dog" in Latin. It was charted by Greek astronomer Ptolemy in the 2nd century. The constellation represents one of the two dogs, the other one being Canis Minor
, that follow Orion
, the hunter. In some myths, the constellation is said to represent Laelaps, a dog that was so fast no prey could outrun it. When it came across a vicious fox that was just as fast, the race could not come to a resolution and Zeus turned both animals to stone, placing the dog in the sky.
The constellation Canis Major occupies an area of 380 square degrees and contains three stars with known planets. It can be seen at latitudes between +60° and -90° and is best visible at 9 p.m. during the month of February.
Canis Major is home to the brightest star in the sky. 
alpha Canis Majoris, better known as Sirius or the "Dog Star," has a visual apparent magnitude of -1.46 and is only 8.6 light-years away from Earth. It can be seen from any part of the Earth except north of 73°. The only objects brighter than Sirius can be found inside our solar system: the Moon, Venus, Jupiter and occasionally Mercury and Mars. Sirius is actually a binary star system, composed of a white main sequence star, Sirius A, and a white dwarf, Sirius B.
The star is quite significant in many different cultures. The Romans used to sacrifice a brown dog at the beginning of the "Dog Days," when the Dog Star rose just before or simultaneously with the Sun (heliacal rising) because they believed that the star was causing the unbearably hot days of summer, between July 24 and August 24, and it needed to be appeased. The period is still sometimes called the Dog Days in a number of European cultures. In Sweden, they call it "Rötmånad" and in Finland, "Mätäkuu," both meaning "rotting month." In parts of India, where the period lasts for 28 days in April or May, they refer to it as "Kathiri veyyil" ("sunlight that acts like scissors") or "Agni Nakshathram" ("star of fire"). In ancient Egypt, the star was used as a flood warning because it appeared just before the season of the Nile’s flooding. The name Sirius itself derives from the Greek word "seirios," meaning glowing, searing or scorching.
Sirius is known under many different names, including Aschere (from the Arabic "al-shira," meaning "leader"), Mrgavyadha ("deer hunter") or Lubdhaka ("hunter") in Sanskrit, Lokabrenna ("Loki’s torch") in Scandinavian countries, Aoboshi ("blue star") in Japan, and the star of the "celestial wolf" in China. Native peoples of North America also had canine names for the star. The Blackfoot called it "Dog-face," the Pawnee referred to it as the "Wolf Star" or "Coyote Star," and the Inuit in Alaska called it "Moon Dog."
Sirius is part of the Winter Hexagon or Winter Circle, an asterism visible from December to March, that it forms with 
Rigel (beta Orionis), 
Aldebaran (alpha Tauri), 
Capella (alpha Aurigae), 
Pollux/Castor (beta and alpha Geminorum) and 
Procyon (alpha Canis Minoris). Another notable asterism is the Winter Triangle, more regularly shaped than the Hexagon. It is formed by 
Procyon and 
Betelgeuse (alpha Orionis), three of the ten brightest objects in the sky that lie outside our solar system.
Other notable stars in Canis Major are 
epsilon Canis Majoris or Adhara ("virgins"), another binary and the second brightest star in the constellation, 
beta Canis Majoris, Mirzam or Murzim ("the herald"), a magnitude 2 blue-white giant, 
delta Canis Majoris or Wezen ("the weight"), a yellow-white supergiant and the third brightest star in Canis Major, 
eta Canis Majoris or Aludra ("the virgin"), a blue supergiant, and 
gamma Canis Majoris or Muliphen ("dog's ear"), a relatively faint blue-white B-type bright giant. Finally, there is 
tau Canis Majoris, an O-type blue supergiant and the brightest star of the open cluster NGC 2362. The tau CMa star system is among the brightest in the galaxy.
Aside from the star cluster NGC 2362, notable deep sky objects in Canis Major include Messier 41, an open cluster with a great number of stars brighter than the Sun within the space of only 25 light-years across, and the Canis Major Dwarf galaxy, an irregular galaxy which is also the closest satellite galaxy to Earth and contains a high percentage of red giants.
Canis Major belongs to the Orion family of constellations, along with Orion
, Canis Minor
Constellations directly bordering Canis Major are Monoceros