Properties
This is a giant star with a stellar classification of K4 III. It is 130 times more luminous than the Sun. Kochab has reached a state in its evolution where the outer envelope has expanded to 42 times the girth of the Sun. This enlarged atmosphere is radiating 390 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 4,030 K. This heat gives the star the orange-hued glow of a K-type star.
By modelling this star based upon evolutionary tracks, the mass of this star can be estimated as 2.2 ± 0.3 that of the Sun. A mass estimate using the interferometrically-measured radius of this star and its spectroscopically-determined surface gravity yields 2.5 ± 0.9 solar masses. The star is known to undergo periodic variations in luminosity over roughly 4.6 days, with the astroseismic frequencies depending sensitively on the star's mass. From this, a much lower mass estimate of 1.3 ± 0.3 solar is reached.
Read more about this topic: Beta Ursae Minoris
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