Circumpolarity of the star

Circumpolarity of the star :

Star rise and set helically for a given place on different dates in a year. In between the helical setting and rising dates the star will not be visible.On the other hand , in between the helical rising and setting the star will be visible in the night sky. in case of some stars once it is set helically on some day , for a long period it will be not visible at all . This period of invisibility can be for several hundreds or thousands of years .depending on the declination of the star and terrestrial latitude of the place.Then the star is said to be 'Circumpolar'.

Whether a star is circumpolar depends upon the observer's latitude.Since the altitude of the north or south celestial pole (whichever is visible) equals the absolute value of the observer's latitude any star whose angular distance from the visible celestial pole is less than the absolute latitude will be circumpolar. For example, if the observer's latitude is 50° N, any star will be circumpolar if it is less than 50° from the north celestial pole. If the observer's latitude is 35° S, then all stars within 35° of the south celestial pole are circumpolar. Stars on the celestial equator are not circumpolar when observed from any latitude in either hemisphere of the Earth.

 "A star with its polar distance approximately equal to or less than the latitude of the observer".

Example : canopus star

                                              -PVGANIGA


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