redshift

red shift

or red·shift (rĕd′shĭft′)n. An increase in the wavelength of radiation emitted by a receding celestial object as a consequence of the Doppler effect.

[From the fact that the longer wavelengths of light are at the red end of the visible spectrum.]

redshift

(ˈrɛdˌʃɪft) n (Astronomy) a shift in the lines of the spectrum of an astronomical object towards a longer wavelength (the red end of an optical spectrum), relative to the wavelength of these lines in the terrestrial spectrum, usually as a result of the Doppler effect caused by the recession of the object. Compare: blueshift

red•shift

(ˈrɛdˌʃɪft)

n. a shift in the spectrum of a celestial object toward longer wavelengths, caused by the object's movement away from the viewer. [1920–25] red′shift`ed, adj.

Thesaurus

Noun

redshift - (astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum); generally interpreted as evidence that the universe is expandingred shiftastronomy, uranology - the branch of physics that studies celestial bodies and the universe as a wholepropagation - the movement of a wave through a medium

Translations

spostamento verso il rosso

redshift

(red -shift) A displacement of spectral lines toward longer wavelength values; for an optical line, the shift would be toward the red end of the visible spectrum. The redshift parameter, z, is given by the ratio δλ/λ, where δλ is the observed increase in wavelength of the radiation and λ is the wavelength of the spectral line at the time of emission from a source, i.e. the wavelength in the ‘normal’ terrestrial spectrum.

The redshifts of astronomical objects within the Galaxy are interpreted as Doppler shifts (see Doppler effect) caused by movement of the source away from the observer. The value of z is then v /c , where v is the relative radial velocity and c is the speed of light. The redshifts of extragalactic sources, including quasars, are also interpreted in terms of the Doppler effect, which for these objects results from the expansion of the Universe. The redshift parameter of a distant galaxy thus gives its velocity of recession; since recessional velocities can be very great, the relativistic expression for redshift must be used: z = [(c + v )/(c – v )]^½ – 1

From measurements of galactic redshifts it has been possible to calculate the distances of galaxies, using Hubble's law (see distance determination).

The redshifts described above represent a loss of energy by the photons of radiation in overcoming the effects of recession or expansion. There is another mechanism, however, by which redshifts can be produced, i.e. by which photons can lose energy – the presence of a strong gravitational field. This gravitational redshift was predicted by Einstein in his general theory of relativity. Although the redshifts of galaxies are often interpreted as being caused by the relativistic Doppler effect alone, both the expansion and the gravitational field of the Universe are involved. See also cosmological redshift.

redshift

[′red‚shift] (astrophysics) A systematic displacement toward longer wavelengths of lines in the spectra of distant galaxies and also of the continuous portion of the spectrum; increases with distance from the observer. Also known as Hubble effect.

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red shift

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red•shift

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Synonyms for redshift

noun (astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum)

Synonyms

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