Kochab

Spectral type: K4 III
U−B color index: +1.78
B−V color index: +1.47
Temperature: 4030 K
Metallicity: [Fe/H] –0.29
Rotational velocity: (v sin i) 8 km/s

Kochab (β UMi, β Ursae Minoris) is a giant star with a stellar classification of K4 III. Kochab has reached a state in its evolution where the outer envelope has expanded. This enlarged atmosphere is radiating luminosity 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.

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.

Etymology

The origin of the name Kochab is from ancient Earth الكوكب al-kawkab "the star", short for الكوكب الشمالي al-kawkab al-šamāliyy "the north star" (lit. heavenly body), a name shared with Polaris. The star is also known as Kocab, Kochah, Beta Ursae Minoris, 7 Ursae Minoris, Al Kaukab al Shamaliyy and 北極二 (Běi Jí èr, the Second Star of North Pole.)