Circumpolar star

A circumpolar star is a star that, as seen from a certain latitude on Earth, never goes below the horizon. This happens because these stars appear close to one of the celestial poles. Because of this, people in some places can see these stars every night of the year. They look like they are moving in circles around the sky, but they never disappear behind the horizon.

All circumpolar stars are inside a circumpolar circle. The size of this circle changes depending on where you are on Earth. The size of the circle is the same as the observer’s latitude. If you are closer to the North or South Pole, the circle grows larger. This means more stars stay above the horizon all the time.

The word "Arctic" used to mean places where some star groups, called the 'bear' constellations (Ursa Major, the Great Bear, and Ursa Minor, the Little Bear), were always visible at night. This name comes from the Greek word ἀρκτικός (arktikos), meaning 'bearish', from ἄρκτος (arktos), which just means 'bear'. These stars have helped people find their way and tell time for a very long time.

Explanation

As Earth rotates, stars appear to move in circles around one of the celestial poles—the north celestial pole for viewers in the Northern Hemisphere and the south celestial pole for those in the Southern Hemisphere. Stars very close to a celestial pole seem to hardly move at all.

Some stars, called circumpolar stars, stay above the horizon all night long because they are close to a celestial pole. From the North Pole, all visible stars are circumpolar. As you move toward the Equator, fewer stars stay above the horizon all night. At the Equator, even the pole star (Polaris) dips below the horizon for part of the day. South of the Equator, the opposite happens, and near the South Pole, most stars are circumpolar again.

Definition

A circumpolar star is a star that never goes below the horizon from a certain place on Earth. This happens because the star is close to one of the celestial poles — either the north or south pole in the sky. Whether a star is circumpolar depends on where you are on Earth. If you live far enough north or south, some stars will always be above the horizon and visible all night.

For example, if you live in a place like London, stars such as Capella and Deneb are always visible and never go below the horizon. Other stars, like Vega, might only seem to set if you are very far north. In places closer to the south pole, stars like [Crux](/wiki/Crux_(constellation are always above the horizon. These stars are special because they are always there, no matter what time of night it is.

Constellations

A circumpolar constellation is a constellation (group of stars) that never goes below the horizon, as seen from a spot on Earth. From places near the North Pole or South Pole, many constellations are always in the sky. But if you are on the Equator, there are no circumpolar constellations.

From places in mid-northern latitudes, such as parts of Europe and North America, some well-known circumpolar constellations are Ursa Major, Ursa Minor, Draco, Cepheus, and Cassiopeia. Other less famous ones are Camelopardalis, Lynx, and Lacerta.