Calculate the cosmological or Doppler redshift (z) and the recession velocity of a distant object.
Last updated: March 2026 | By ForgeCalc Engineering
Redshift occurs when the light from an object is increased in wavelength, or shifted to the red end of the spectrum. In astronomy, this is usually caused by the Doppler effect (motion through space) or cosmological expansion (expansion of space itself).
By measuring the shift of known spectral lines (like Hydrogen alpha), astronomers can determine how fast a galaxy is moving away from us and, by extension, how far away it is using Hubble's Law.
Blueshift is the opposite of redshift. It occurs when an object is moving toward the observer, causing the wavelength to decrease (shift toward the blue end).
Yes. For very distant galaxies, z can be much greater than 1. This means the observed wavelength is more than twice the emitted wavelength.
The simple v = zc formula is only accurate for small z (z < 0.1). For larger z, relativistic formulas must be used.
The most distant known galaxies have redshifts exceeding z = 10, meaning we are seeing them as they were just a few hundred million years after the Big Bang.
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