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Hence, in Anaximanders's cosmogony, in the beginning was the sphere, out of which celestial rings were formed, from some of which the stellar sphere was in turn composed. As viewed from the Earth, the ring of the Sun was highest, that of the Moon was lower, and the sphere of the stars was lowest.
At their intersections with the celestial sphere, these form the celestial equator, the north and south celestial poles, and the ecliptic, respectively. [8] As the celestial sphere is considered arbitrary or infinite in radius, all observers see the celestial equator, celestial poles, and ecliptic at the same place against the background stars.
A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. [1] The first constellations were likely defined in prehistory. People used them to relate stories of their beliefs, experiences, creation, and ...
The term night sky refers to the sky as seen at night. The term is usually associated with skygazing and astronomy, with reference to views of celestial bodies such as stars, the Moon, and planets that become visible on a clear night after the Sun has set. Natural light sources in a night sky include moonlight, starlight, and airglow, depending ...
Bayer's naming convention has been in use since 1603, and consists of a Greek letter combined with the possessive form of the star's constellation. [1] Both names are shown for each star in the tables and charts below. Each star's approximate position on the celestial sphere is given using the equatorial coordinate system.
Early astronomers recognized a difference between "fixed stars", whose position on the celestial sphere does not change, and "wandering stars" , which move noticeably relative to the fixed stars over days or weeks. [6] Many ancient astronomers believed that the stars were permanently affixed to a heavenly sphere and that they were immutable.
The unaided human eye can perceive about 6,000 stars, of which about half are below the horizon at any one time. On modern star charts, the celestial sphere is divided into 88 constellations. Every star lies within a constellation. Constellations are useful for navigation. Polaris lies nearly due north to an observer in the Northern Hemisphere.
The southern celestial hemisphere, also called the Southern Sky, is the southern half of the celestial sphere; that is, it lies south of the celestial equator. This arbitrary sphere, on which seemingly fixed stars form constellations, appears to rotate westward around a polar axis as the Earth rotates.