In a sky full of gods, heroes and wronged women, there are also four dogs. We have Canis Minor and the two dogs of Canes Venatici, but Canis Major is definitely top dog. It's a prominent constellation that has represented a dog from early Greek times.

Canis Major - the Greater Dog

The open star cluster Messier 41 is the only Messier object in Canis Major. (Photo: Anthony Ayiomamitis) It's 25 light years in diameter and contains around a hundred stars with a mixture of blue, yellow and orange stars.

Galaxy or Star Cluster? will tell you about what an open star cluster is.

Sirius is a bright star with a long history. There was no thought of its being a binary system until the mid-19th century. German astronomer Friedrich Besserl (1784-1846) concluded in 1844 that Sirius had an unseen companion. But it wasn't until 1862 that the companion was seen. In 1862 American telescope-maker Alvan Clark saw it. In this photograph you can see Sirius A and Sirius B. Sirius B is a white dwarf. It's the little dot below bright Sirius A and slightly to the left of center.

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Canis Major depicted on a celestial globe known as the Manuchihr Globe. It was commissioned by Abu al-Fatḥ Manuchihr Khan, Governor of Khurasan in Mashhad, Persia 1632-33.

Photo: Adlinor Collection, Sweden