FN Canis Majoris

FN Canis Majoris is a binary star system in the southern constellation Canis Major, near the northern constellation border with Monoceros. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.41. The system is located at a distance of approximately 3,000 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +31 km/s. It is a runaway star associated with the Sh 2-296 nebula in the CMa OB1 association, and has a conspicuous bow-shock feature.

The brighter component is a visual magnitude 5.69 B-type star that has been assigned various stellar classification from B0 III/IV to B2 Ia/ab, suggesting it is an evolved state. In the past it was classified as a Beta Cephei type variable star with an apparent magnitude that was measured varing between +5.38 and +5.42 over a period of 36.7 hours, but is no longer considered to be one. This is a massive star with estimates ranging from 19 to 36 times the mass of the Sun, and luminosity estimates of 122,079 to 690,000 times the Sun's luminosity. The magnitude 7.04 companion is located at an angular separation of $0.033$ from the primary at a position angle of 111°, as of 2003.