Circumpolar star

In astronomy refers to a specific place on earth those astronomical objects as circumpolar ( from Latin circum, " around ", and Greek polos, " eddy "), which are located near the celestial pole and not perish. In the context of stars is called Zirkumpolarsternen, in connection with constellations of Zirkumpolarsternbildern.

As the earth rotates, the sky objects describe seemingly circular orbits whose centers lie on the extended axis of the earth ( the celestial axis ).

At observation sites in the northern hemisphere of the earth with latitude φ are objects whose declination is greater than 90 ° - φ, circumpolar. Analogously, objects with a declination less -90 ° φ circumpolar at observation sites in the southern hemisphere ( southern latitude with a negative value ). Objects whose orbit intersects the horizon will be temporarily disappear among them, thus under - and rise again.

For the northern hemisphere goes for circumpolar objects:

(90 ° - φ ) < δ <90 °

And for the southern hemisphere:

-90 ° < δ <- (90 ° φ )

At the north and south poles all visible, extrasolar objects in the sky are circumpolar, the Earth's equator, however, no. Between the poles and the equator increases towards the equator from the proportion of circumpolar objects.

Of great importance for the geographical and temporal orientation have always been certain stars of Zirkumpolarregion, as they are visible at night throughout the year.

On the northern hemisphere the polar star, and thus the direction North is determined as follows:

• The North Star is the main star of the Ursa Minor ( Little Dipper ), which is not as easy to spot as its larger neighbors Ursa Major ( Big Dipper ) and the constellation Cassiopeia.
• The Little Bear ( and thus also the Pole Star ) is located approximately in the middle between Cassiopeia and the Big Dipper.
• The distance between the rear box stars of the Big Dipper is extended five times to get to the position of the Polar Star.