An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 16 Search : coordinates
astronomical coordinates
  هماراها‌ی اخترشناسیک، ~ اخترشناختی   
hamârâhâ-ye axtaršenâsik, ~ axtarsršnâxti (#)

Fr.: coordonnées astronomiques   

Values in a reference system used to relate the position of a body on the celestial sphere.

astronomical; → coordinates.

canonical coordinates
  هماراها‌یِ هنجاروار   
hamârâhâ-ye hanjârvâr,

Fr.: coordonnées canoniques   

Any set of generalized coordinates of a system together with their → conjugate momenta.

canonical; → coordinates.

Cartesian coordinates
  هم‌آراهای ِ دکارتی   
hamârâhâ-ye Dekârti

Fr.: coordonnées cartésiennes   

A → coordinate system in which the position of a point is specified by two (in a plane) or three (in 3-dimensional space) → real numbers representing the distances from two perpendicular axes or from three perpendicular planes, respectively. René Descartes (1596-1650) introduced the coordinates system in his La Géométrie in 1637.

Cartesian; → coordinate.

celestial coordinates
  هماراهای ِ آسمانی   
hamârâhâ-ye âsmâni (#)

Fr.: coordonées célestes   

Any system of coordinates used to define a point on the celestial sphere (zenith distance, altitude, celestial latitude, celestial longitude, etc.).

celestial; → coordinates.

comoving coordinates
  هماراهای ِ هم‌جنب   
hamârâhâ-ye hamjonb

Fr.: coordonnées comobiles   

A system of coordinates used in cosmology which is fixed with respect to the overall → Hubble flow of the universe. A given galaxy's location in comoving coordinates does not change as the Universe expands.

comoving; → frame.

cylindrical coordinates
  هماراهای ِ استوانه‌ای   
hamârâhâ-ye ostovâne-yi (#)

Fr.: coordonnées cylindriques   

A coordinate system for a point in space, using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which a point (P) in space is specified by three numbers ρ, φ, z. The two first numbers, ρ and φ, are → polar coordinates for the vertical projection of P on the xy-plane, and z is the vertical distance of P from the xy-plane.

cylindrical; → coordinate.

equatorial coordinates
  هماراها‌ی ِ هموگاری   
hamârâhâ-ye hamugâri

Fr.: coordonnées équatoriales   

Celestial coordinates in the → equator system.

equatorial, → coordinate.

Galactic coordinates
  هماراهای ِ کهکشانی   
hamârâhâ-ye kahkešâni

Fr.: coordonnées galactiques   

A system of astronomical coordinates using → latitude (bII) measured north and south from the → Galactic equator and → longitude (lII), measured from the → Galactic Center in the sense of increasing → right ascension from 0 to 360 degrees. In the old system (lI,bI), the Galactic center was at lI = 327°41'. Same as → galactic system.

galactic; → coordinate.

GCN: The Gamma-ray Coordinates Network
  توربست ِ هماراهای ِ پرتوهای ِ گاما   
turbast-e hamârâhâ-ye partowhâ-ye gâmâ

Fr.: Le réseau des coordonnées des rayons gamma   

A follow-up community network concerned with → gamma-ray burst (GRB)s. It deals with: 1) locations of GRBs and other → transients detected by spacecraft (most in real-time while the GRB is still bursting), and 2) reports of follow-up observations (the Circulars) made by ground-based and space-based optical, radio, X-ray, TeV, and other observers. The GCN Circulars allow the GRB follow-up community to make optimum use of its limited resources (labor and telescope time) by communicating what has already been done or will soon be done.

gamma ray; → coordinate; → network.

generalized coordinates
  هماراهای ِ هروینیده   
hamârâhâ-ye harvinidé

Fr.: coordonnées généralisées   

In a material system, the independent parameters which completely specify the configuration of the system, i.e. the position of its particles with respect to the frame of reference. Usually each coordinate is designated by the letter q with a numerical subscript. A set of generalized coordinates would be written as q1, q2, ..., qn. Thus a particle moving in a plane may be described by two coordinates q1, q2, which may in special cases be the → Cartesian coordinates x, y, or the → polar coordinates r, θ, or any other suitable pair of coordinates. A particle moving in a space is located by three coordinates, which may be Cartesian coordinates x, y, z, or → spherical coordinates r, θ, φ, or in general q1, q2, q3. The generalized coordinates are normally a "minimal set" of coordinates. For example, in Cartesian coordinates the simple pendulum requires two coordinates (x and y), but in polar coordinates only one coordinate (θ) is required. So θ is the appropriate generalized coordinate for the pendulum problem.

generalized; → coordinate.

geodetic coordinates
  هماراهای ِ زمین‌سنجیک   
hamârâhâ-ye zamin-sanjik

Fr.: coordonnées géodésiques   

A → coordinate system, composed of → geodetic latitude and → geodetic longitude on the → Earth's surface which is dependent on the figure and size of a particular model for the Earth's surface.

geodetic; → coordinate.

polar coordinates
  هم‌آراهای ِ قطبی   
hamârâhâ-ye qotbi (#)

Fr.: coordonnées polaires   

A coordinate system in which the position of any point (M) in a plane is specified by two coordinates: 1) ρ, which expresses the distance from a fixed point (the pole, denoted O), and 2) the number φ, which is the angle formed by the line segment OM and a fixed reference line passing through the pole.

polar; → coordinate.

precessed coordinates
  هم‌آراهای ِ پیشایانیده   
hamârâhâ-ye pišâyânidé

Fr.: coordonnées précessées, ~ corrigées de la précession   

The apparent position of a celestial object corrected for the epoch → precession.

Precessed, p.p. of → precess; → coordinates.

Rindler coordinates
  هماراهای ِ ریندلر   
hamârâhâ-ye Rindler

Fr.: coordonnées de Rindler   

The coordinates that describe the → Minkowski space-time in a → hyperbolic version of → polar coordinates. If the coordinates in an → inertial frame is denoted by (t,x), the Rindler coordinates (η,ξ) are defined by: t = (1/α) eαξ sinh (αη) and x = (1/α) eαξ cosh (αη), where α is some positive constant.

Named after Wolfgang Rindler (1924-), Austrian physicist; → coordinates.

spherical coordinates
  هماراها‌ی ِ کره‌ای   
hamârâhâ-ye kore-yi

Fr.: coordonnées sphériques   

A coordinate system using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which the position of a point (P) is given by three numbers (r, θ, φ). The coordinate r is the distance from the origin, θ the angle between the z-axis and the r direction, and φ the angle between the projection of r on the xy-plane and the Ox-axis. The coordinate φ is also called the → azimuthal angle.

spherical; → coordinate.

topocentric coordinates
  هماراهای ِ جا-مرکزی   
hamârâhâ-ye jâ-markazi

Fr.: coordonées topocentriques   

A coordinate system that uses the observer's location as its central reference point. Usually, the difference in the position of an object in the sky measured using topocentric and geocentric coordinates is very small because most celestial objects are so far away. However, for nearby objects this is not true. The Sun, for example, may appear displaced as much as eight arcseconds from its geocentric position, and the Moon by as much as one degree.

Topocentric, from topo- combining form of Gk. topos "place" + centric, from → center; → coordinate.

Hamârâhâ, → coordinate; jâ-markazi "topocentric," from "place" (from Mid.Pers. giyâg "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night") + markazi, of, pertaining to markaz, → center.