Canis Major, the Greater Dog, is a southern constellation that represents one of Orion's hunting dogs. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Along with Canis Minor (the Lesser Dog), Canis Major follows faithfully behind Orion in the sky. Alpha Canis Majoris is Sirius, the Dog Star. In Greek, name Sirius means "Searing" or "Scorching." Sirius is the brightest star in the night sky at mag -1.44. It is a spectral-class A-type blue-white star that is located only 8.6 light-years away from the Earth. Sirius is a binary star with a white dwarf companion, Sirius B, named the "Pup". It is a magnitude 8.44 star that lies close to Sirius making it difficult to observe in a telescope because of the primary's great brilliance. The pair have an orbital period of 50 years. They were closest, separated by 3 arcseconds, in 1994. They will be farthest apart in 2019 when they will be separated by 11 arcseconds. Canis Major contains only one Messier object - open cluster M41. It also contains NGC 2362, the Tau Canis Majoris open cluster and the emission / reflection nebula complex NGC 2359, Thor's Helmet. M46 and M47 are also visible in the image, just over the border in Puppis. The large emission nebula IC 2177, the Seagull Nebula, is located on the Canis Major - Monoceros border. Canis Major was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 43rd largest of today's 88 modern constellations, covering 380 square degrees of sky. North is to the top in the above image.
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