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Last updated on April 19, 2014 at 8:45 EDT

Circumpolar Star

Circumpolar Star — Circumpolar stars are those stars which are located near the poles of the celestial sphere. As the Earth rotates, the sky appears to rotate; and most stars will be hidden below the horizon at some point in their circular paths.

A circumpolar star is near enough to the celestial pole that it will never go under the horizon. It will therefore be visibile for all the night, and for the entire year.

Such a definition implies that different stars can be defined as circumpolar at different Earth latitudes. For example, to an observer place right at the Earth’s North or South Pole, virtually all the stars are circumpolars.

For an observer exactly on the equator, no star can be defined circumpolar, as the pole itself is on the horizon. At different latitudes, an intermediate situation makes some stars circumpolars and others not.

An example is Polaris.

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NASA

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Circumpolar Star