Assertion: star | /r/HasProperty | circumpolar
Facets:
value: for an observer
type: PURPOSE
value: for some observer
type: TRANSITIVE-OBJECT
value: at latitude φ
type: OTHER
value: in one hemisphere
type: LOCATION
value: at the equator
type: LOCATION
Source sentences:
text: All stars which are neither circumpolar nor never visible will have their upper transit above and their lower transit below horizon, and thus rise and set during a siderial day.
text: Some stars within the far northern constellation (such as Cassiopeia, Cepheus, Ursa Major, and Ursa Minor) roughly north of the Tropic of Cancer (+23½°) will be circumpolar stars, which never rise or set.
text: Depending on the observer's latitude on Earth, some stars – the circumpolar ones – are close enough to the celestial pole to remain continuously above the horizon, while other stars dip below the horizon for some portion of their daily circular path (and others remain permanently below the horizon).
text: The stars of the first group are called circumpolar stars.
text: At the Earth's North Pole, the north celestial pole is directly overhead, and all stars that are visible at all (that is, all stars in the Northern Celestial Hemisphere) are circumpolar.
text: Whether a star is circumpolar depends upon the observer's latitude.
text: 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.
text: If the observer's latitude is 35° S, then all stars within 35° of the south celestial pole are circumpolar.
text: The star is circumpolar if θ + δ is greater than +90° (observer in Northern Hemisphere), or θ
text: At the equator no star is circumpolar.
text: At the North or South Pole all stars that are visible at all are circumpolar, since only one half of the celestial sphere can ever be seen.
text: Stars (and constellations) that are circumpolar in one hemisphere are always invisible in the high latitudes of the opposite hemisphere, and these never rise above the horizon.
text: Generally, if a star whose declination is δ is circumpolar for some observer (where δ is either positive or negative), then a star whose declination is −δ never rises above the horizon, as seen by the same observer.
text: Likewise, if a star is circumpolar for an observer at latitude φ, then it never rises above the horizon as seen by an observer at latitude −φ.
text: Some stars within the far southern constellations (such as Crux, Musca, and Hydrus) roughly south of the Tropic of Capricorn (−23½°) will also be circumpolar stars.