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 Template:Solar mass and a young age of 35Template:Nbspmillion years, while Earle Luck gives a smaller mass of Template:Solar mass and a higher age of 1.05Template:Nbspbillion years. The effective temperature of the star is of 3,980Template:NbspK, which gives it an 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 Template:Solar radius and a luminosity of Template:Solar luminosity. Assuming it is a giant, Earle Luck gives a much lower luminosity of Template:Solar luminosity with a corresponding radius of Template:Solar radius.Template:Efn By the distance implied by its Gaia DR2 parallax, it would have a luminosity of Template:Solar luminosity, rather high for a giant. An older measurement based on the Hipparcos distance of Template:Convert give a lower luminosity of Template:Solar luminosity.

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 Template:Val. The two stars appear to be unrelated and the close alignment accidental, with HD 56578 being a much closer and less luminous Am star.