145 G. Canis Majoris

145 G. Canis Majoris (HD 56577) is a single K giant or supergiant star in the southern constellation of Canis Major. This star is Gould's 145th of Canis Major in his Uranometria Argentina. Kostjuk erroneously lists it as simply "145 CMa". SIMBAD follows this error in its object query result as "* 145 CMa – Star".

The properties and evolutionary state of 145 G. CMa are disputed, it being classed either as a young massive supergiant or a somewhat older and less massive giant. It has been given two MK spectral classifications: K3Ib (corresponding to a supergiant) and K4III (corresponding to a giant). Tezzlaff et al. gives a large mass of and a young age of 35million years, while Earle Luck gives a smaller mass of  and a higher age of 1.05billion years. The effective temperature of the star is of 3,980K, which gives it a orange hue typical of K-type stars.

Based on the assumption that it is a supergiant, 145 CMa has been given a large radius of and a luminosity of. Assuming it is a giant, Earle Luck give a much lower luminosity of with a corresponding radius of. By the distance implied by its Gaia DR2 parallax, it would have a luminosity of, rather high for a giant. An older measurement based on the Hipparcos distance of 435 pc give a lower luminosity of.

The star is one component of a close double, the other being HD 56578 which on its own would be a faint naked-eye star. The two are separated by $28.05$. The two stars appear to be unrelated and the close alignment accidental, with HD 56578 being a much closer and less luminous Am star.