Redshift
Article
Redshift is the displacement of spectral features toward longer wavelengths compared with their laboratory values. It is commonly expressed by the dimensionless quantity z, which compares the observed and emitted wavelengths.
Redshift can be produced by motion away from the observer through the Doppler effect, by the expansion of the universe, or by light escaping from a gravitational field. These mechanisms are physically distinct but can produce similar changes in wavelength.
Cosmological redshift increases with the expansion of space between emission and observation. For nearby galaxies it is approximately proportional to distance through the Hubble relation, while greater distances require a cosmological model.
Astronomers measure redshifts from absorption and emission lines to estimate velocities, distances, cosmic epochs, and the motion of gas and stars. Blueshift is the corresponding movement toward shorter wavelengths.
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- Source / publisher: Wikipedia
- URL type: WWW
- Credits: Wikipedia
- URL: https://en.wikipedia.org/wiki/Redshift