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The redshift observed in astronomy can be measured because the emission and absorption spectra for atoms are distinctive and well known, calibrated from spectroscopic experiments in laboratories on Earth. When the redshift of various absorption and emission lines from a single astronomical object is measured, z is found
The cosmic ionization history is generally described in terms of the free electron fraction x e as a function of redshift. It is the ratio of the abundance of free electrons to the total abundance of hydrogen (both neutral and ionized).
Redshift can be measured by determining the wavelength of a known transition, such as hydrogen α-lines for distant quasars, and finding the fractional shift compared to a stationary reference. Thus, redshift is a quantity unambiguously acquired from observation.
Redshift quantization, also referred to as redshift periodicity, [1] redshift discretization, [2] preferred redshifts [3] and redshift-magnitude bands, [4] [5] is the hypothesis that the redshifts of cosmologically distant objects (in particular galaxies and quasars) tend to cluster around multiples of some particular value.
I.E. the adjustment to the standard relationship between absolute and apparent magnitude required to correct for the redshift effect. [4] Here, D L is the luminosity distance measured in parsecs . The exact nature of the calculation that needs to be applied in order to perform a K correction depends upon the type of filter used to make the ...
One application of Hubble's law is to estimate distances to galaxies based on measurements of their recessional velocities. However, for relatively nearby galaxies the peculiar velocity can be comparable to or larger than the recessional velocity, in which case Hubble's law does not give a good estimate of an object's distance based on its ...
Evidence now shows strong evolution in the Lyman-alpha escape fraction with redshift, most likely associated with the buildup of dust in the ISM. Dust is shown to be the main parameter setting the escape of Lyman-alpha photons. [4] Additionally the metallicity, outflows, and detailed evolution with redshift is unknown.
Spectral lines of their light can be used to determine their redshift. For supernovae at redshift less than around 0.1, or light travel time less than 10 percent of the age of the universe, this gives a nearly linear distance–redshift relation due to Hubble's law. At larger distances, since the expansion rate of the universe has changed over ...