An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < Alf Lag Sou > >>

Number of Results: 55 Search : point
Lagrangian point
  نقطه‌های ِ لاگرانژ   
noqtehâ-ye Lagrange (#)

Fr.: points de Lagrange   

On of the five locations in space where the → centrifugal force and the → gravitational force of two bodies (m orbiting M) neutralize each other. A third, less massive body, located at any one of these points, will be held in equilibrium with respect to the other two. Three of the points, L1, L2, and L3, lie on a line joining the centers of M and m. L1 lies between M and m, near to m, L2 lies beyond m, and L3 on the other side of M beyond the orbit. The other two points, L4 and L5, which are the most stable, lie on either side of this line, in the orbit of m around M, each of them making an equilateral triangle with M and m. L4 lies in the m's orbit approximately 60° ahead of it, while L5 lies in the m's orbit approximately 60° behind m. See also → Trojan asteroid; → Roche lobe; → equipotential surface; → horseshoe orbit.

Lagrangian; → point.

lambda point
  نقطه‌ی ِ لامبدا   
noqte-ye lâmbdâ

Fr.: point lambda   

The temperature (roughly 2.17 K) at which → liquid helium (→ helium I) becomes → superfluid (→ helium II).

The name was given by the Dutch physicist Willem Hendrik Keesom (1876-1956), who discovered the behavior of helium near this transition point and successfully solidified helium in 1926 (under an external pressure of 25 atmospheres). The name was originally suggested by Paul Ehrenfest (1880-1933), who was inspired by the shape of the → specific heat curve, which resembles the Gk. letter → lambda; → point.

magnetic null point
  نقطه‌ی ِ نول ِ مغناتیسی   
noqte-ye nul-e meqnâtisi

Fr.: point nul magnétique   

A region of the → solar corona where the → magnetic field vanishes.

magnetic; → null; → point.

melting point
  نقطه‌ی ِ گداز   
noqte-ye godâz (#)

Fr.: point de fusion   

The temperature at which a solid changes to a liquid.

melting; → point.

neutral point
  نقطه‌ی ِ نتار   
noqte-ye natâr

Fr.: point neutre   

1) A point where two fields are equal in magnitude and opposite in direction so that the net force exerted on it is zero.
2) One of several points in the sky for which the → degree of polarization of diffuse sky light is zero.

neutral; → point.

nodal point
  نقطه‌ی ِ گرهی   
noqte-ye gerehi

Fr.: point nodal   

Any of the two points on the → axis of a → lens system, such that if the → incident ray passes through one, travelling in a given direction, the → emergent ray passes the other in a parallel direction.

nodal; → point.

North point
  نقطه‌ی ِ هودر   
noqte-ye hudar

Fr.: point Nord   

The point on → horizon in direction of → geographic north pole.

north; → point.

  نقطه‌ی ِ O   
noqte-te O

Fr.: point O   

The circular configuration of magnetic field lines around a → magnetic null point. See also → X-point.

O, the round letter of alphabet; → point.

ordinary point
  نقطه‌ی ِ شونیک   
noqte-ye šunik

Fr.: point ordinaire   

The point M0(x0,y0) of the curve F(x,y) = 0, where at least one of the partial derivatives ∂F/∂x and ∂F/∂y does not vanish. → singular point

ordinary; → point.

  ۱) نقطه، پنده؛ ۲) آماجیدن   
1) noqté (#), pandé (#); 2) âmâjidan

Fr.: 1) point; 2) pointer   

1a) General: A sharp or tapering end, as of a dagger; a projecting part of anything.
1b) Physics: Position or time of occurrence, as in boiling point, freezing point, etc.
1c) Math.: A dimensionless geometric element whose location in space is defined solely by its coordinates.
2) To direct a telescope toward a particular position on the sky.

M.E. point(e); O.Fr. point "dot, mark, place, moment;" L. punctum noun use of neuter p.p. of pungere "to prick, pierce."

1) Noqté, loan from Ar. Pandé, variants in classical dictionaries pindé, pendé, fand "a point, dot, mole, freckle;" cf. Skt. prānta- "point, tip, border," from pra "before, forward," → pro-, + ánta- "end, limit, term;" Pali, panta- "remote, solitary;" Prakrit panta " last;" Sindhi pandu "border of a garment;" Lahnda pand, pad "end, top of sugar cane."
2) Âmâjidan, verb from âmâj "aim, goal," from Proto-Iranian base *āma-, from prefix *ā- + *ma- "to measure;" cf. Av. mati- "point, tip;" O.Pers./Av. mā(y)- "to measure;" Pers. mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl;" cf. Skt. mati "measures," matra- "measure," Gk. metron "measure," L. metrum; PIE base *me- "to measure."

point mass
  نقطه‌جرم، پنده‌جرم، جرم ِ نقطه‌وار، ~ پنده‌وار   
noqté jerm, pandé jerm, jerm-e noqtevâr, ~ pandevâr

Fr.: masse ponctuelle   

A hypothetical object which can be thought of as infinitely small.

point; → mass.

point source
  نقطه‌خن، پنده‌خن، خن ِ نقطه‌وار، ~ پنده‌وار   
noqté xan, pandé xan, xan-e noqtevâr, pande-ye ~

Fr.: source ponctuelle   

A source of radiation at a great distance from the observer; an ideal source of infinitesimal size.

point; → source.

point spread function (PSF)
  کریای ِ گسترش ِ نقطه، ~ ~ پنده   
karyâ-ye gostareš-e noqté, ~ ~ pandé

Fr.: fonction d'étalement du point   

The two-dimensional intensity distribution about the image of a point source.

point; → spread; → function.



The two stars that form the front of the Big Dipper's bowl, away from the handle. More specifically, the stars Dubhe (α Ursae Majoris) and Merak (β Ursae Majoris). A line through β to α passes close to the North Star and they are used for finding it.

point + -er.

Dorahnemâ, literally "the two guides," from do "two" + rah, râh "way, path" (from Mid.Pers. râh, râs "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" L. rota "wheel," rotare "to revolve, roll;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE *roto- "to run, to turn, to roll") + nemâ agent noun of nemudan "to show" (Mid.Pers. nimūdan, nimây- "to show," from O.Pers./Av. ni- "down; into" (Skt. ni "down," nitaram "downward," Gk. neiothen "from below," cf. E. nether, O.E. niþera, neoþera "down, downward, below, beneath," from P.Gmc. *nitheraz, Du. neder, Ger. nieder; PIE *ni- "down, below") + māy- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure").


Fr.: pointage   

The act or process of directing a telescope. → point.
The direction in the sky to which the telescope is pointed. Pointing also describes how accurately a telescope can be pointed toward a particular direction in the sky.

Verbal noun of → point.

pointing model
  مدل ِ آماجش   
model-e âmâješ

Fr.: modèle de pointage   

A mathematical model that reproduces the diurnal rotation of the Earth and is used to direct a telescope toward a precise position on the sky.

pointing; → model.

sample point
  نقطه‌ی ِ نمونان   
noqte-ye nemunân

Fr.: point de l'échantillon   

Statistics: Each possible outcome in a → sample space.

sample; → point.

singular point
  نقطه‌ی ِ تکین   
noqte-ye takin

Fr.: point singulier   

The point M0(x0,y0) of the curve F(x,y) = 0, where at least one of the → partial derivatives ∂F/∂x and ∂F/∂y vanishes. See also → ordinary point.

singular; → point.

solsticial points
  نقطه‌های ِ خوریستانی   
noqtehâ-ye xoristâni

Fr.: points solsticiaux   

The two points of the ecliptic the most distant from the equator.

Solsticial, adj. of → solstice; → point.

sonic point
  نقطه‌ی ِ صدایی   
noqte-ye sedâyi

Fr.: point sonique   

The point where the → stellar wind makes a transition from → subsonic to → supersonic flow. In the particular case of a spherically symmetric wind (thus with no magnetic field), the distance from star, at which the sonic point occurs, is given by: rs = (GM*)/2cs2, where G is the → gravitational constant, M* is the stellar mass, and cs the → sound speed at the sonic point.

sonic; → point.

<< < Alf Lag Sou > >>