Though relatively young in stellar terms (probably less than twenty million years old), Omicron1Canis Majoris is a massivestar that has burned through its hydrogen and is now fusing helium in its core. In the process it has expanded to become a supergiant so huge that, if lay at the centre of the Solar System, its outer shell would lie beyond the orbit of Mars. It is some ten thousand times more luminous than the Sun in visual wavelengths.
The star almost directly northward of Omicron1Canis Majoris is the hot Wolf-Rayet star EZ Canis Majoris, surrounded by a faint bubble nebula. The arc of this nebula can be seen extending outward as far as Omicron1, which appears to interact with its expanding gases. Imagery provided by Aladin sky atlas
Omicron1Canis Majoris is a very distant star, lying so far away that its precise distance is difficult to calculate. Early estimates placed it 2,000 light years or more from the Solar System, but more recent parallax data suggests that it is a little closer than this, and probably falls some 1,300 light years from the Sun.