Mu Velorum
Binary star in the constellation Vela
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Mu Velorum (μ Vel, μ Velorum) is a binary star system in the southern constellation Vela. The pair have a combined apparent visual magnitude of 2.69,[2] making the system readily visible to the naked eye. From parallax measurements, the distance to this system is measured at 117 light-years (36 parsecs).[1]
Characteristics
The two stars orbit each other with a period of 138 years and a very high eccentricity of 0.94. Their semi-major axis is of 50 astronomical units,[a] but due to this high eccentricity the separation at periastron is just 3.1 au, while at the apoastron their separation is about 100 au.[b] The system is about 360 million years old.[3]
The primary component is a giant star with an apparent magnitude of 2.7 and a stellar classification of G5 III.[3] It is radiating about 107 times the luminosity of the Sun from an expanded atmosphere about 13 times the Sun's radius.[8] The mass of this star is 3.3 times that of the Sun.[7] In 1998, the Extreme Ultraviolet Explorer space telescope detected a strong flare that released an X-ray emission nearly equal to the output of the entire star. The quiescent X-ray luminosity of Mu Velorum A is about 1.7 × 1030 erg s−1.[3]
The fainter companion, Mu Velorum B, is a main sequence star with an apparent magnitude of 6.4[3] and an assigned stellar classification of G2V.[3] However, this classification is suspect. Closer examination of the spectrum suggests the star may actually have a classification of F4V or F5V, which suggests a mass of about 1.5 times the mass of the Sun. Such stars typically do not show a marked level of magnetic activity.[3]