Talk:Alpha Mensae

Mass/Luminosity discrepancy

Alpha Mensae is a bit of an anomaly. It is about 10% more massive than the sun and slightly older. Therefore, it should be decidedly more evolved. The spectral type is in close agreement here (0.5 classes cooler) but the luminosity is below the solar value. Even if we use the rule of thumb, that luminosity is proportional to m^3.5, and disregard hydrogen depletion, Alpha Mensae should have >1.35 times the sun's luminosity. The imminent giant phase exacerbates that further. Is there any mention of that issue in scientific literature or papers, which could add to the article and explain why alpha Mensae is rather dim? - ¡Ouch! (^{hurt me} / _{more pain}) 15:36, 23 June 2017 (UTC)

You're not comparing like with like. Even though the mass and luminosity (to take two values that you mention) are taken from the same published paper, they are not determined using the same methodology and should not be compared with eachother. The luminosity is a direct observational value, give or take some assumptions about distance, extinction, etc. The given mass is an "isochrone mass", a theoretical mass for a star with the given observed temperature, luminosity, and elemental abundances. Conveniently in this case the same paper also calculates spectroscopic masses, effectively a directly observed mass calculated from the surface gravity and radius. It notes that the modelled "isochrone" masses are systematically 10% larger than the "observed" spectroscopic masses. This sort of result is part of the constant feedback between stellar evolutionary models and observations of real stars. In particular, for α Mensae the isochrone mass quoted in the article is larger than the sun's while the spectroscopic mass is smaller. Lithopsian (talk) 18:41, 23 June 2017 (UTC)

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