Galaxy Recession Velocity

The Galaxy Recession Velocity calculator computes the velocity of a galaxy away from Earth based on the redshift and the speed of light. 

INSTRUCTIONS: Enter the following:

• (z) Redshift

Recession Velocity (V):  The calculator returns the velocity in kilometers per second.  However, this can be automatically converted to compatible units via the pull-down menu. 

The Math / Science

Red Shift is used to compute the recession velocity of a galaxy.  The formula for the recession velocity of a galaxy is:

`V = z*C` 

where:

• V = recession velocity
• z = redshift
• C = Speed of Light

A source of light moving toward or away from an observer will have it's spectrum shifted toward the blue (moving toward) or to the red (moving away). This formula gives the magnitude of the wavelength shift given the speed of the source relative to the observer (for speeds well below the speed of light only!).

The formula for Redshift is:

      z = (λ_v - λ₀) / λ₀

where:

• z = red shift
• λv = Observed Wavelength
• λ0 = Resting Wavelength

Astronomy Calculators

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• Astronomical Distance Travel Time Calculator computes the time to travel to distant parts of space at different velocities.
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