red shift definition of red shift in the Free Online Encyclopedia.

red shift or redshift, in astronomy, the systematic displacement of individual lines in the spectrum spectrum, 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
..... Click the link for more information. of a celestial object toward the red, or longer wavelength, end of the visible spectrum. The effect was discovered by V. M. Slipher Earl C. Slipher, 1883–1964, was a noted planetary astronomer who also worked at the Lowell Observatory. His many years of observations of the planet Mars were published in 1962 as The Photographic Story of Mars.
..... Click the link for more information. of Lowell Observatory. Some red shifts are the result of the Doppler effect Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is named for the Austrian scientist Christian Doppler, who demonstrated
..... Click the link for more information. , i.e., of the relative motion of the earth and the object away from each other. The amount of displacement is a function of the object's recessional velocity relative to the observer. All distant galaxies show a red shift proportional to their distance from the earth as a result of the general expansion of space-time (see Hubble's law Hubble's law, in astronomy, statement that the distances between galaxies (see galaxy ) or clusters of galaxies are continuously increasing and that therefore the universe is expanding.
..... Click the link for more information. ). Known as the cosmological red shift, this results when the wavelength of light is stretched as it moves through the expanding universe. Red shifts are also produced by gravitation (the gravitational red shift) in accordance with the general theory of relativity relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference.
..... Click the link for more information. . Because of the strong gravitational field, the frequency of the light emitted by atoms in a dense, compact star will be lower and the wavelengths consequently longer; such effects have been observed in white dwarfs white dwarf, in astronomy, a type of star that is abnormally faint for its white-hot temperature (see mass-luminosity relation ). Typically, a white dwarf star has the mass of the sun and the radius of the earth but does not emit enough light or other radiation to be
..... Click the link for more information. . Not all celestial bodies have spectra displaced toward the red end of the spectrum. Of the billions of known galaxies, about 100—for example, the Andromeda Galaxy Andromeda Galaxy, cataloged as M31 and NGC 224, the closest large galaxy to the Milky Way and the only one visible to the naked eye in the Northern Hemisphere. It is also known as the Great Nebula in Andromeda. It is 2.
..... Click the link for more information. —are blue-shifted, indicating that they are approaching earth rather than receding from it. Most of these are dwarf galaxies in Milky Way's Local Group and in orbit about one another. See also blue shift blue shift or blueshift, in astronomy, the systematic displacement of individual lines in the spectrum of a celestial object toward the blue, or shorter wavelength, end of the visible spectrum.
..... Click the link for more information. ; cosmology cosmology, area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe .

Modern Cosmological Theories

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