redshift
Noun: 1. (Astronomy) A shift in the spectral lines of light from distant celestial objects (such as galaxies or stars) toward longer wavelengths, which is the red end of the visible spectrum. This phenomenon is a key piece of observational evidence supporting the theory that the universe is expanding.
Redshift is a specific scientific measurement used to determine the velocity and distance of astronomical objects moving away from an observer. * The greater the redshift of a galaxy, the faster it is receding from us and, according to Hubble's law, the farther away it is. * Astronomers measured the redshift of the quasar to calculate its immense distance from Earth.
- Cosmological Redshift: The primary type of redshift caused by the expansion of the universe itself, which stretches the wavelength of light as it travels through space.
- The cosmological redshift of the cosmic microwave background radiation is a direct remnant of the Big Bang.
- Doppler Redshift: A shift caused by the relative motion of an object moving away from the observer. While often discussed conceptually for astronomical objects, the cosmological redshift is distinct from a simple Doppler effect on the scale of the universe.
- Gravitational Redshift: A shift caused by light escaping a strong gravitational field, such as that near a black hole. This is a prediction of Einstein's general theory of relativity.
- Blueshift (noun): The opposite phenomenon, where spectral lines shift toward shorter (blue) wavelengths, indicating an object is moving toward the observer.
- The measured blueshift of the Andromeda Galaxy shows it is moving toward our Milky Way.
- Redshifted (adjective): Describes light or an object that has undergone redshift.
- The light from that galaxy is highly redshifted.
- Doppler shift (when referring specifically to the shift due to relative radial motion, though note the distinction in cosmology).
- Hubble's Law: The observational principle in cosmology that states the velocity at which a galaxy recedes is proportional to its distance from us, with redshift serving as the measure of that velocity.
- Hubble's Law uses redshift as a proxy for recessional velocity.
- Spectroscopy: The scientific technique of analyzing light spectra, which is used to measure redshift.
- Accurate redshift measurements depend on precise spectroscopy.
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(astronomy) a shift in the spectra of very distant galaxies toward longer wavelengths (toward the red end of the spectrum); generally interpreted as evidence that the universe is expanding
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