redshift

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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.
References in periodicals archive ?
The research concludes that the cosmic red-shift effect is not evidence of an expanding Universe but is an indicator for the distance to the light's source - light coming from more distant stars passes through more gravitational spheres, resulting in statistically greater red-shift.
It is notable that the red-shift in the PL emission spectra of the nanocomposites was only observed when a large amount of epoxy resin penetrated into the clay agglomerates (OMMT and HNTs) independently of the presence of intercalated clay structures (MMT and OMMT), as noticed by AFM images.
Thus, analysis of structural, electronic and, principally vibrational parameters, using DFT hybrid functionals, may produce satisfactory results, not only for red-shift interactions, but also for the blue-shift hydrogen-bond type.
Such a red-shift would mean that the quasars were enormously distant, over a billion light-years away, and the fact that they could be seen at all at such a distance meant they were unusual indeed.
It can be found that these compounds having red-shift in tetrahydrofuran are shown in Fig-4 and Table-1.
Both UV-vis absorption and PL emission peaks of the DtBP-PPV exhibit a red-shift phenomenon as compared with those of the DO-PPV.
Although the group has not directly measured the distances, the researchers estimate that one galaxy has a red-shift of 8 and lies 14.
Calculating the work done by the radiation-radiation interaction on a photon, we can obtain a radiation red-shift.
If the number of bumps is increased, the magnitude of the extinction cross section increases, and the extinction cross section is broadened with a slightly larger red-shift and more pronounced broadening, due to the thinning of the nano-shell, which leads to a plasmon resonance red-shift [47].
This method is independent of red-shift, so the distance measurement is not contaminated by a galaxy's unknown orbital motion in the grip of a cluster's gravitational field.
The ZITs refer to an interesting time, ascosmologists describe it, back at a red-shift of 1,000.