Redshift

The Redshift calculator computes the astronomical redshift (z) based on the resting and observed wavelength of light.

INSTRUCTIONS: Choose units and enter the following:

• (λ_v) Observed Wavelength of Light
• (λ₀) Resting Wavelength of Light from Emitting Source w/o any velocity shift.

Red Shift(z):  The calculator returns the red shift factor as a real number, and the implied relative velocity (v) in meters per second.

The Math / Science

The formula for Redshift is:

      z = (λ_v - λ₀) / λ₀

where:

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

Red Shift is often used to compute the recession velocity of a galaxy.

V = z*C 

• V = 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!).

Astronomy Calculators