Celestial sphere

The celestial sphere is divided by the celestial equator. The celestial equator is a Great circle on the imaginary Celestial sphere, in the same plane as the Earth 's Equator.

This article is about modern uses of the celestial sphere in astronomy and navigation. For material celestial spheres from Antiquity to the Renaissance, see Celestial spheres. The celestial spheres or celestial orbs were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle

In astronomy and navigation, the celestial sphere is an imaginary rotating sphere of "gigantic radius", concentric and coaxial with the Earth. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study Navigation is the process of reading and controlling the movement of a craft or vehicle from one place to another Imagination is the ability to form Mental images/sounds/feelings or the ability to Spontaneously Generate images/sounds/feelings within one's own Mind A rotation is a movement of an object in a circular motion A two- Dimensional object rotates around a center (or point) of rotation "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe Remote Authentication Dial In User Service ( RADIUS) is a networking protocol that provides centralized access authorization and accounting management for people or computers Concentric objects share the same center, axis or origin with one inside the other In Geometry, coaxial means that two or more forms share a common axis; it is the three- Dimensional linear analog of " Concentric " EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 All objects in the sky can be thought of as lying upon the sphere. The sky is the part of the Atmosphere or of Outer space visible from the surface of any Astronomical object. Projected from their corresponding geographic equivalents are the celestial equator and the celestial poles. Geography (from Greek γεωγραφία - geografia) is the study of the Earth and its lands features inhabitants and phenomena The celestial equator is a Great circle on the imaginary Celestial sphere, in the same plane as the Earth 's Equator. The north and south celestial poles are the two imaginary points in the sky where the Earth's Axis of rotation, "infinitely extended" intersects the The celestial sphere projection is a very practical tool for positional astronomy. Spherical astronomy or positional astronomy is the branch of Astronomy that is used to determine the location of objects on the Celestial sphere, as seen

The celestial sphere can be used geocentrically and topocentrically. In Astronomy, the geocentric model of the Universe is the superseded theory that the Earth is the center of the universe and other The former means that it is centred upon an imaginary observer in the centre of the Earth, and no parallax effects need to be taken into account. Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between In the latter case it is centred upon an observer on the surface of the Earth and then horizontal parallax cannot always be ignored; especially not for the Moon. In Astronomy, Geography, Geometry and related sciences and contexts a plane is said to be horizontal at a given point if it is locally Parallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between

In the Aristotelic and Ptolemaic models, the celestial sphere was imagined as a physical reality rather than a geometrical projection (see Celestial spheres). Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. The celestial spheres or celestial orbs were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle

The celestial sphere is divided by projecting the equator into space. The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the This divides the sphere into the north celestial hemisphere and the south celestial hemisphere. Likewise, one can locate the Celestial Tropic of Cancer, Celestial Tropic of Capricorn, North Celestial Pole, and South Celestial Pole. The directions toward various objects in the sky can be quantified by constructing a celestial coordinate system. In Astronomy, a celestial coordinate system is a Coordinate system for mapping positions in the sky

As the Earth rotates from west to east around its axis once every 23 hours 56 minutes, the celestial sphere and all objects on it appear to rotate from east to west around the celestial poles in the same time. This article refers to the cardinal direction for other uses see West (disambiguation. The Experimental Advanced Superconducting Tokamak (EAST internal designation HT-7U is an experimental Superconducting Tokamak Magnetic fusion energy The Experimental Advanced Superconducting Tokamak (EAST internal designation HT-7U is an experimental Superconducting Tokamak Magnetic fusion energy This article refers to the cardinal direction for other uses see West (disambiguation. The north and south celestial poles are the two imaginary points in the sky where the Earth's Axis of rotation, "infinitely extended" intersects the This is the diurnal motion. Diurnal motion is an astronomical term referring to the apparent daily motion of Stars around the Earth, or more precisely around the two Therefore stars will rise in the east, culminate on the north-south line (meridian) and set in the west, (unless a star is circumpolar). This article is about the astronomical concept For other uses of the word see Meridian. A circumpolar star is a star that as viewed from a given latitude on Earth never sets (that is never disappears below the horizon due to its proximity to one of the Celestial On the next night a particular star will rise again, but with our normal clocks running a 24 hour 0 minutes cycle, it will do so 4 minutes earlier. By the following night the difference will be 8 minutes, and so forth with every following night (or day).

The reason for this apparent misadjustment of our clocks is that the Sun is not standing still on the celestial sphere, as the stars do, but moves about 1° per day eastwards over a great circle known as the ecliptic (which is 360° or a full circle in one year, the annual motion of the Sun). A great circle is a Circle on the surface of a Sphere that has the same circumference as the sphere dividing the sphere into two equal Hemispheres. The ecliptic is the apparent path that the Sun traces out in the sky during the year As an angle of 1° corresponds to 4 minutes in time (360° = 24 hours), we need therefore 4 extra minutes of diurnal motion to see the Sun back on (for example) the meridian again, making the duration of one rotation just 24 hours exactly (on the average, ignoring small seasonal variations, see equation of time)

Normal clocks therefore indicate solar time. The equation of time is the difference over the course of a year between time as read from a Sundial and time as read from a Clock, measured in an ideal situation Solar times are measures of the apparent position of the Sun on the Celestial sphere. Astronomers studying the movements of stars may want clocks indicating sidereal time, going around once in 23h56m (solar time units). Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Sidereal time is a measure of the position of the Earth in its rotation around its axis or time measured by the apparent Diurnal motion of the Vernal equinox

A celestial sphere can also refer to a physical model of the celestial sphere. Also known as a star globe, this sort of celestial sphere will indicate which constellations are visible at a given time and place.

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In Astronomy, a celestial coordinate system is a Coordinate system for mapping positions in the sky The celestial equator is a Great circle on the imaginary Celestial sphere, in the same plane as the Earth 's Equator. The celestial horizon, also called the rational horizon, is a Great circle parallel to the Horizon, the center of which is the center of the The north and south celestial poles are the two imaginary points in the sky where the Earth's Axis of rotation, "infinitely extended" intersects the The celestial spheres or celestial orbs were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle In Mathematics, conformal geometry is the study of the set of angle-preserving ( conformal) transformations on a Riemannian manifold or Pseudo-Riemannian An equinox is the event of the Sun passing over the Earth's equator in its annual cycle In Astronomy, the geocentric model of the Universe is the superseded theory that the Earth is the center of the universe and other The North Star is the prominent Pole star that lies closest in the sky to the north celestial pole and which appears (approximately directly overhead to A pole star is a visible star especially a prominent one that is approximately aligned with the Earth 's Axis of rotation; that is a star whose apparent position Direct motion is the motion of a Planetary body in a direction similar to that of other bodies within its system and is sometimes called prograde motion. Setting circles are used on Telescopes equipped with an Equatorial mount to find astronomical objects in the sky by their equatorial coordinates often used Solstices occur twice a year when the tilt of the Earth's axis is most oriented toward or away from the Sun, causing the Sun to reach its northernmost and southernmost extremes A modern invention the term South Star, also called southern Pole star, refers to the Star that happens to lie closest to the south Celestial pole The concept of a spherical Earth dates back to around the 6th century BC in ancient Greek philosophy and possibly ancient Indian philosophy. Zodiac denotes an annual cycle of twelve stations along the Ecliptic, the apparent path of the sun across the heavens through the Constellations that divide the ecliptic

Dictionary

-noun

(astronomy) An abstract sphere of infinite radius which serves as the imaginary backdrop for celestial objects, and of which the visible sky is one hemisphere.

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