Circumpolar stars are those stars which are located near the celestial poles of the celestial sphere, i.e. the poles in the equatorial coordinate system. 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. If, from a certain location, a star is near enough to the celestial pole that it never appears to go "under the horizon"; it will therefore be visible (from said location) for the entire night, on every day of the year. Some of the circumpolar stars nearest the poles do not seem to engage in diurnal motion at all. For instance, a stargazer in Ohio will never be able to see a star far enough south of the celestial equator to be circumpolar. The two celestial poles are the imaginary points where the Earths spin axis intersects the imaginary rotating sphere of gigantic radius, called the celestial sphere. ... The celestial sphere is divided by the celestial equator. ... The equatorial coordinate system is probably the most widely used celestial coordinate system, whose equatorial coordinates are: declination () right ascension () -also RA-, or hour angle () -also HA- It is the most closely related to the geographic coordinate system, because they use the same fundamental plane, and the same poles. ... Horizon. ... The two celestial poles are the imaginary points where the Earths spin axis intersects the imaginary rotating sphere of gigantic radius, called the celestial sphere. ... Diurnal motion is an astronomical term referring to the apparent daily motion of stars in orbit around the Earth, caused by the Earths rotation around its axis. ...

The North Star and circumpolar stars

Such a definition implies that different stars can be defined as circumpolar at different Earth latitudes. For example, to an observer placed 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. Image File history File links Download high resolution version (3008x2080, 966 KB) Circumpolar stars, self-made, License: File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Archaeoastronomy Circumpolar star ... Image File history File links Download high resolution version (3008x2080, 966 KB) Circumpolar stars, self-made, License: File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Archaeoastronomy Circumpolar star ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... North Pole Scenery When not otherwise qualified, the term North Pole usually refers to the Geographic North Pole – the northernmost point on the surface of the Earth, where the Earths axis of rotation intersects the Earths surface. ... Amundsen-Scott South Pole Station. ... World map showing the equator in red The Equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ...

Some astronomers define a circumpolar star as any star having a declination of 55 or more degrees from the celestial equator; i.e., a declination between 55° and 90° on the celestial sphere. In other words, circumpolar stars are generally within 35° of the north or south celestial pole. These astronomers propose this idea because, from the vantange point of stargazers outside of the tropics, most stars with declinations between 55° and 90° never rise or set on the horizon in their respective hemispheres. Stars of extreme northern constellations, such as Cassiopeia, Cepheus, Ursa Major, and Ursa Minor are well within this zone. Observers living in mid-northern latitudes always see the stars of these constellations above the horizon, never rising or setting. Stars of extreme southern constellations, such as Crux, Carina, and Hydrus are also well within this zone of circumpolar stars. Observers living in mid-southern latitudes, in countries such as Australia, South Africa, and Argentina, always see the stars of these constellations above the horizon. From their vantange point, the diurnal circles of these extreme southern stars do not cross below the horizon; therefore, they never rise or set. Stars and constellations that are circumpolar (within 35° of the celestial pole) in one hemisphere are virtually invisible, never rising above the horizon, in the middle and high latitudes of the opposite hemisphere. For example, the southern circumpolar star Acrux is invisible from most the Continental United States, likewise, the seven stars of the northern circumpolar Big Dipper asterism are invisible from most of the Patagonia region of South America. An astronomer or astrophysicist is a person whose area of interest is astronomy or astrophysics. ... In astronomy, declination (abbrev. ... The celestial equator is a great circle on the imaginary celestial sphere, which could be constructed by inflating the Earths equator until it intersects with said sphere. ... A frame of reference is a particular perspective from which the universe is observed. ... A stargazer is a person who observes the stars, planets and other celestial objects or phenomena on a regular basis, whether it be for scientific study or for recreation. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern hemisphere. ... The word hemisphere literally means half sphere or half ball; when used in the singular form, it refers to one of the halves of a spherical object. ... This article or section does not cite its references or sources. ... Cassiopeia is a northern constellation which Greek mythology considered to represent a vain queen. ... Cepheus (IPA: ) is a northern constellation named after King Cepheus in Greek mythology, and is considered to represent a king. ... Ursa Major is a constellation visible throughout the year in the northern hemisphere. ... Ursa Minor is a constellation in the northern sky, the name of which means Small Bear in Latin. ... Crux, being Latin for cross, commonly known as the Southern Cross (in contrast to the Northern Cross), is the smallest of the 88 modern constellations, but also one of the most famous. ... Cheese wizz rulz hardcore. ... Hydrus (Latin for Hydra, also referred to as male Hydra or little Hydra) is a minor southern constellation. ... Diurnal motion is an astronomical term referring to the apparent daily motion of stars in orbit around the Earth, caused by the Earths rotation around its axis. ... Acrux (α Cru / α Crucis / Alpha Crucis) is the brightest star in constellation Crux (the Southern Cross) and the thirteenth brightest star in the nighttime sky, at visual magnitude 0. ... Depending on usage, the term continental United States can refer to either: the 48 contiguous states plus the District of Columbia; or the 48 contiguous states plus the District of Columbia and Alaska. ... Big Dipper map The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial. ... Asterism has several meanings: In astronomy, it refers to a constellation_like group of stars; see asterism (astronomy) In gemmology, it is an optical phenomenon; see asterism (gemmology) In typography, it refers to a symbol; see asterism (typography) This is a disambiguation page — a navigational aid which lists other pages... In orange the area most commonly defined as Patagonia. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ...

On the northern hemisphere all circumpolar stars rotate around the North Star Polaris, which itself is almost stationary, always at the north (i.e., the azimuth is 0°), and always at the same altitude (angle from the horizon), equal to the latitude of the point of observation on Earth. The North Star is a title of the star best suited for navigation northwards. ... For other uses, see Polaris (disambiguation). ... Azimuth is the horizontal component of a direction (compass direction), measured around the horizon, usually from the north toward the east — i. ... Altitude is the elevation of an object from a known level or datum. ... Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator. ...

External links

• Bartleby.com: Circumpolar Star
• North Circumpolar Star Trails
• South Circumpolar Star Trails