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Overview

redshift

Any shift of the peaks of a spectrum to longer wavelengths (i.e. towards the red end of the spectrum), including a shift from the red to infrared. Compare blue shift.

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redshift

redshift   Quick reference

A Dictionary of Space Exploration (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...redshift The lengthening of the wavelengths of light from an object as a result of the object's motion away from us. It is an example of the Doppler effect . The redshift in light from galaxies is evidence that the Universe is expanding. Lengthening of wavelengths causes the light to move or shift towards the red end of the spectrum , hence the name. The amount of redshift can be measured by the displacement of lines in an object's spectrum. By measuring the amount of redshift in light from stars and galaxies, astronomers can tell how quickly these objects...

redshift

redshift   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018
Subject:
Science and technology, Astronomy and Cosmology
Length:
471 words
Illustration(s):
2

... ( symbol z ) The amount by which the wavelength of light from a receding object is lengthened (i.e. moved to the red) by the Doppler shift . Redshift is calculated from the formula z = Δ λ / λ , where λ ‎ is the original wavelength (as measured in the laboratory) and Δ ‎ λ ‎ the observed change in wavelength. A redshift of 0.1, for example, means that the light has been redshifted by 10% in wavelength, whereas a redshift of 1 means a change of 100% (i.e. a doubling in wavelength). All galaxies at large distances from our own have redshifts...

redshift

redshift   Quick reference

A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
217 words

...see relativistic speed ). The redshift of spectral lines occurs in all regions of the electromagnetic spectrum; ultraviolet can be shifted into the visible region and visible radiation can be shifted into the infrared region. 2. ( gravitational redshift or Einstein redshift ) A similar displacement of spectral lines towards the red caused not by a Doppler effect but by a high gravitational field. This type of redshift was predicted by Einstein and some astronomers believe that this is the cause of the large redshifts of quasars , which can be as...

redshift

redshift   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Astronomy and Cosmology
Length:
892 words
Illustration(s):
3

...objects at redshift z ≪ 1, redshift is often quoted in units of km/s, i.e. as a recession velocity. In this case, the velocity quoted is the product of redshift multiplied by the speed of light c : υ = cz . Redshift proper, being a ratio of two wavelengths, is a dimensionless quantity, and so has no units. Redshift as evolution of density Yet another use of the word ‘redshift’ is to describe how the density of material varies as the Universe expands. For instance, one may see the density of non-relativistic matter described as redshifting as a 3 as...

redshift survey

redshift survey   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

... survey A compilation of the redshifts of a large number of galaxies, or other extragalactic objects, selected according to certain criteria. Such surveys may be used to map out the large-scale structure of the Universe or to investigate galaxy evolution . Redshift surveys are important because it is very difficult to measure true distances of all but the closest galaxies. It is relatively easy, however, to measure a galaxy’s redshift and hence its velocity of recession. For nearby galaxies (redshift 0.1 and less), there is a simple relation...

redshift space

redshift space   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

... space Redshift space is the name given to the coordinate system in which the distance to an extra-Galactic object, such as a galaxy , is determined from its redshift . Relative to real space, which uses true distances, redshift space is distorted by peculiar velocities . These are velocities relative to the Hubble expansion . Since only the radial coordinate is affected, structures which are intrinsically isotropic appear to be anisotropic in redshift space. Redshift space is distorted on both small and large scales. On small scales, galaxies...

photometric redshift

photometric redshift   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Astronomy and Cosmology
Length:
348 words
Illustration(s):
1

...the overall shape of an object's spectrum to estimate a photometric redshift. This technique is less accurate than spectroscopy , since the overall spectral shape of a galaxy is affected by its stellar population as well as redshift. One thus needs to determine the object's type concurrently with its redshift: there is often a degeneracy between the two. There are two classes of techniques currently in use for estimating photometric redshifts from broad-band photometric observations. The first class, template fitting methods, assume that the distribution of...

gravitational redshift

gravitational redshift   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...redshift The redshift of light or other electromagnetic radiation caused by a strong gravitational field; also known as the Einstein shift . It arises because radiation loses energy as it passes out of the gravitational field of the emitting body. As a consequence, the frequency of the radiation decreases and its wavelength is shifted to the red end of the spectrum. The redshift at wavelength λ ‎ is given by Gm λ ‎/ c 2 r , where m is the mass of the body, r is the distance of the emitting region from the centre of mass, c is the speed of...

redshift surveys

redshift surveys   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Astronomy and Cosmology
Length:
3,185 words
Illustration(s):
1

...low redshifts. Relativistic expressions relating distance to redshift have been derived which are valid for any measured redshift and which depend on the assumed cosmological parameters . Fig. 1. Spectrum of a galaxy at redshift z = 0.2038 as observed (on the right) and as it would be seen at redshift zero (on the left). Note that the distinctive absorption features (dips) in the spectrum are shifted to higher wavelengths by a factor of (1 + z ). galaxy spectrum Jon Loveday History of redshift surveys Three techniques have been used to compile redshift...

redshift–magnitude relation

redshift–magnitude relation   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...–magnitude relation The relationship between the observed redshift and apparent magnitude of an object with known absolute magnitude in the expanding Universe. The predicted relationship is different for different cosmological models ( see hubble diagram...

redshift–distance relation

redshift–distance relation   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

...–distance relation A formula relating the observed redshift of an extragalactic object to its distance in the expanding Universe. For redshifts of about 0.1 or less, this relationship is linear and appears as a straight line on the Hubble diagram . The relationship does not hold for objects so close together that their mutual gravitational attraction overrides the expansion of the Universe (e.g. galaxies in a cluster), nor for galaxies very close to us which may even show a blueshift. For redshifts much larger than 0.1, the relation becomes non-linear,...

CfA Redshift Survey

CfA Redshift Survey   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

...Redshift Survey The Center for Astrophysics ( CfA ) Redshift Survey was started in 1977 and the first part was completed in 1982 . It contained redshifts for 2 401 galaxies brighter than magnitude 14.5 at high Galactic latitude in the merged catalogues of Zwicky and Nilson , and produced the first large area and moderately deep three-dimensional maps of cosmic structure in the nearby Universe. The second CfA survey (CfA2), carried out between 1985 and 1995 , extended the original CfA survey one magnitude fainter and contains redshifts for...

two degree field galaxy redshift survey

two degree field galaxy redshift survey   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

...Due to the expansion of the Universe , light from a distant object will be stretched to redder wavelengths. By measuring the redshift of spectral features of known rest wavelength, a distance to the object may be estimated. This enables observers to map out the three-dimensional distribution of galaxies in space. The 2dFGRS, carried out in conjunction with the two degree field quasar redshift survey (2QZ), has measured redshifts of 221 414 galaxies selected from the APM galaxy survey. Important scientific results to emerge from the 2dFGRS include: • an...

two degree field quasar redshift survey

two degree field quasar redshift survey   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

...degree field quasar redshift survey ( 2QZ ) The two degree field quasar redshift survey maps the distribution of 23 424 quasars in two 75 degress s by 5 degress s stripes in the northern and southern Galactic caps. It was carried out using the two degree field (2dF) multi-object spectrograph on the Anglo-Australian Telescope, New South Wales, concurrently with the two degree field galaxy redshift survey (2dFGRS). Quasar candidates were identified by multicolour selection techniques using digitized, wide-field photographic plates in ultra-violet ( U ),...

redshift

redshift   Reference library

The New Oxford Dictionary for Scientific Writers and Editors (2 ed.)

Reference type:
Subject Reference
Current Version:
2009

... (one word) ...

redshift

redshift noun   Quick reference

New Oxford American Dictionary (3 ed.)

Reference type:
English Dictionary
Current Version:
2015
Subject:
English Dictionaries and Thesauri
Length:
83 words
redshift

redshift  

Any shift of the peaks of a spectrum to longer wavelengths (i.e. towards the red end of the spectrum), including a shift from the red to infrared. Compare blue shift.[...]
photometric redshift

photometric redshift  

Determination of an accurate redshift for an astronomical source requires observation of the object's spectrum, so that the wavelengths of spectral features may be measured. Such observations are ...
redshift space

redshift space  

Redshift space is the name given to the coordinate system in which the distance to an extra-Galactic object, such as a galaxy, is determined from its redshift. Relative to real ...
redshift survey

redshift survey  

A compilation of the redshifts of a large number of galaxies, or other extragalactic objects, selected according to certain criteria. Such surveys may be used to map out the large-scale structure of ...

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