Ursa Minor


Ursa Minor


English nameLesser Bear, Little Bear or Little Dipper

Major
stars
alpha Ursae MinorisPolarismagn. 2,1RA: 02h 31m 48.28sDec: +89 15' 50.7"
beta Ursae MinorisKochabmagn. 2,2RA: 14h 50m 42.39sDec: +74 09' 19.7"
gamma Ursae MinorisPherkadmagn. 3,1RA: 15h 20m 43.73sDec: +71 50' 02.5"

DescriptionThe constellation of Ursa Minor, though not very brilliant, is important since it contains the North Pole, indicated by Polaris, the principal star of the constellation.

Polaris is a yellow supergiant which is about 600 light-years away: it is not exactly at the North Pole, but it is at a distance of less than one degree; because of the precession, however, it is approaching the Pole (it will return to get further after 2100). Polaris is a variable star, which oscillates between magnitude 2,1 and 2,2 with a period of about 4 days, and besides it is a double star, considering that it has a companion of ninth magnitude.


Mythology
and history
According to Aratus, the constellation represents one of the two nymphs who raised the new-born Zeus: in particular it is Ida, while the other, Adrastea, is identified in Ursa Maior.


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