parallax

par·al·lax

P0059600 (păr′ə-lăks′)n. A change in the apparent position of an object relative to more distant objects, caused by a change in the observer's line of sight toward the object.

[French parallaxe, from Greek parallaxis, from parallassein, to change : para-, among; see para-¹ + allassein, to exchange (from allos, other; see al- in Indo-European roots).]

par′al·lac′tic (-lăk′tĭk) adj.

parallax

(ˈpærəˌlæks) n1. (General Physics) an apparent change in the position of an object resulting from a change in position of the observer2. (Astronomy) astronomy the angle subtended at a celestial body, esp a star, by the radius of the earth's orbit. Annual or heliocentric parallax is the apparent displacement of a nearby star resulting from its observation from the earth. Diurnal or geocentric parallax results from the observation of a planet, the sun, or the moon from the surface of the earth[C17: via French from New Latin parallaxis, from Greek: change, from parallassein to change, from para-¹ + allassein to alter] parallactic adj ˌparalˈlactically adv

par•al•lax

(ˈpær əˌlæks)

n. 1. the apparent displacement of an observed object due to a change in the position of the observer. 2. the apparent angular displacement of a celestial body due to its being observed from the surface instead of from the center of the earth or due to its being observed from the earth instead of from the sun. 3. the difference between the view of an object as seen through the picture-taking lens of a camera and the view as seen through a separate viewfinder. [1585–95; < Greek parállaxis change =parallak- (s. of parallássein to cause to alternate =para- para-¹ + allássein to vary, akin to állos other) + -sis -sis] par`al•lac′tic (-ˈlæk tɪk) adj.

parallaxViewed from point A, a nearby star appears to occupy position a against a background of more distant stars. Six months later, from position B, the star appears to occupy position b.

par·al·lax

(păr′ə-lăks′) An apparent change in the position of an object, such as a star, caused by a change in the observer's position that provides a new line of sight. The parallax of nearby stars caused by observing them from opposite points in Earth's orbit around the sun is used in estimating the stars' distance from Earth.

parallax

In photography, the apparent displacement of the position of an object in relation to a reference point, due to a change in the point of observation.

Thesaurus

Noun

parallax - the apparent displacement of an object as seen from two different points that are not on a line with the objectoptical phenomenon - a physical phenomenon related to or involving lightannual parallax, heliocentric parallax - the parallax of a celestial body using two points in the earth's orbit around the sun as the baselinediurnal parallax, geocentric parallax - the parallax of a celestial body using two points on the surface of the earth as the earth rotates

Translations

parallasse

parallax

(pâr`əlăks), any alteration in the relative apparent positions of objects produced by a shift in the position of the observer. In astronomy the term is used for several techniques for determining distance. Trigonometric parallax is the apparent displacement of a nearby star against the background of more distant stars resulting from the motion of the earth in its orbit around the sun. Formally, the parallax of a star is the angle at the star that is subtended by the mean distance between the earth and the sun. A shift in the angular position of a star will be greatest when observed at intervals of six months; this makes the parallax equal to the value of one half of the semiannual displacement of the star. If a star's parallax can be measured, it then determines the distance to the star. A unit of stellar measurement is the parsecparsec
[parallax + second], in astronomy, basic unit of length for measuring interstellar and intergalactic distances, equal to 206,265 times the distance from the earth to the sun, 3.26 light-years, or 3.08 × 10¹³ km (about 19 million million mi).
..... Click the link for more information. ; it is the distance at which a star would have a parallax of one second of arc and is equivalent to 206,265 times the distance from the earth to the sun, or about 3.3 light-years. A star's distance d in parsecs is the reciprocal of its parallax p (or d = 1/p). The first stellar parallax was measured in 1838 by Friedrich Bessel for the star 61 Cygni. Its parallax of 0.3 places it at a distance of 3.3 parsecs or about 11 light-years. The technique of stellar parallax is useful for stars within 100 parsecs. Spectroscopic parallax is the most widely used technique for determining the distances of stars that are too distant for their stellar parallaxes to be measured. From the analysis of a star's spectrumspectrum,
arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other property. Beams of charged particles can be separated into a spectrum according to mass in a mass spectrometer (see mass spectrograph).
..... Click the link for more information. , its position on the Hertzsprung-Russell diagramHertzsprung-Russell diagram
[for Ejnar Hertzsprung and H. N. Russell], graph showing the luminosity of a star as a function of its surface temperature. The luminosity, or absolute magnitude, increases upwards on the vertical axis; the temperature (or some temperature-dependent
..... Click the link for more information. is determined. This diagram correlates the spectral classspectral class,
in astronomy, a classification of the stars by their spectrum and luminosity. In 1885, E. C. Pickering began the first extensive attempt to classify the stars spectroscopically.
..... Click the link for more information. of the star with its absolute magnitudemagnitude,
in astronomy, measure of the brightness of a star or other celestial object. The stars cataloged by Ptolemy (2d cent. A.D.), all visible with the unaided eye, were ranked on a brightness scale such that the brightest stars were of 1st magnitude and the dimmest stars
..... Click the link for more information. . By comparing the absolute magnitude to its apparent brightness, the star's distance is calculated. Dynamical parallax is a method for determining the distance to a visual binary starbinary star
or binary system,
pair of stars that are held together by their mutual gravitational attraction and revolve about their common center of mass. In 1650 Riccioli made the first binary system discovery, that of the middle star in the Big Dipper's handle, Zeta
..... Click the link for more information. . The angular diameter of the orbit of the stars around each other and their apparent brightness are observed. By applying Kepler's lawsKepler's laws,
three mathematical statements formulated by the German astronomer Johannes Kepler that accurately describe the revolutions of the planets around the sun. Kepler's laws opened the way for the development of celestial mechanics, i.e.
..... Click the link for more information. and the mass-luminosity relationmass-luminosity relation,
in astronomy, law stating that the luminosity of a star is proportional to some power of the mass of the star. More massive stars are in general more luminous.
..... Click the link for more information. , the distance of the binary star can be determined. Geocentric parallax is a technique similar to stellar parallax, which uses the diameter of the earth rather than the diameter of its orbit as a baseline. Because this baseline is relatively small, the technique is useful only for close celestial objects such as the moon or the asteroids.

Parallax.

i. As it relates to photo interpretation, the apparent displacement of the position of a body with respect to a reference point or system caused by a shift in the point of observation. In the illustration, A will see the black post to the right of the white post; the camera at B will see the black post to the left of the white post.
ii. The difference in the direction of a celestial object as seen by an observer from two widely separated points. The measurement of parallax is used directly to find the distance of the body from the earth and from the sun.
iii. The phenomenon in radar imagery when a tall object is imaged and the top of the object is nearer the aircraft. In this case, the slant range to the top of the object is less than that to the base. The object appears to lie toward the aircraft flight path. This is known as radar parallax.

parallax

1. an apparent change in the position of an object resulting from a change in position of the observer 2. Astronomy the angle subtended at a celestial body, esp a star, by the radius of the earth's orbit. Annual or heliocentric parallax is the apparent displacement of a nearby star resulting from its observation from the earth. Diurnal or geocentric parallax results from the observation of a planet, the sun, or the moon from the surface of the earth

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Words related to parallax

noun the apparent displacement of an object as seen from two different points that are not on a line with the object

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