Beta Ursae Minoris
Encyclopedia
Beta Ursae Minoris (β UMi, β Ursae Minoris) is the second brightest star in the bowl of the "Little Dipper,"
the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

 Ursa Minor
Ursa Minor
Ursa Minor , also known as the Little Bear, is a constellation in the northern sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, whence the name Little Dipper...

. It has the traditional name Kochab. Kochab's magnitude is 2.07. It is 16 degrees from Polaris. The star is an orange giant and is 126.4 ± 2.5 light years from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. It is 130 times more luminous than the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. Kochab has a surface temperature of approximately 4,000 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...

.

Kochab and its neighbor Pherkad are both naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...

 stars and are sometimes referred to as the "Guardians of the Pole". They served as twin pole stars, Earth's North pole stars, from 1500 BC until 500 AD. Neither star was as proximitous to the pole as Polaris is now. Due to precession of the equinoxes
Precession of the equinoxes
In astronomy, axial precession is a gravity-induced, slow and continuous change in the orientation of an astronomical body's rotational axis. In particular, it refers to the gradual shift in the orientation of Earth's axis of rotation, which, like a wobbling top, traces out a pair of cones joined...

, the previous holder of the title was Thuban
Thuban
Thuban also known by its Bayer designation Alpha Draconis is a star in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star in ancient times...

, and the next was the present-day Polaris
Polaris
Polaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....

. This succession of pole stars is a result of earth's precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

al motion.

The origin of the name Kochab is unclear. It comes from the Hebrew
Hebrew language
Hebrew is a Semitic language of the Afroasiatic language family. Culturally, is it considered by Jews and other religious groups as the language of the Jewish people, though other Jewish languages had originated among diaspora Jews, and the Hebrew language is also used by non-Jewish groups, such...

 word for star, "kokhav", כוכב. It appears to be cognate with Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...

 الكوكب al-kawkab "the star", short for الكوكب الشمالي al-kawkab al-šamāliyy "the north star" (lit. heavenly body), named when it was still the pole star
Pole star
The term "Pole Star" usually refers to Polaris, which is the current northern pole star, also known as the North Star.In general, however, a pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent...

.

In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...

, , meaning North Pole
Purple Forbidden enclosure
The Purple Forbidden enclosure is one of the San Yuan or Three enclosures. Stars and constellations of this group lie near the north celestial pole and visible all year from temperate latitudes in the Northern Hemisphere.-Asterisms:The asterisms are :...

, refers to an asterism consisting of β Ursae Minoris, γ Ursae Minoris
Gamma Ursae Minoris
Gamma Ursae Minoris is a slightly variable star in the constellation Ursa Minor. It also has the common name Pherkad. Together with Beta Ursae Minoris, Gamma forms the end of the dipper pan of the "Little Dipper"...

, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694. Consequently, β Ursae Minoris itself is known as , representing , meaning Emperor.
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