Astro Doppler Shift Calculator

The observed redshift or blueshift of celestial objects is governed by the Doppler effect, scaled for relativistic velocities. By comparing rest and observed wavelengths, one derives the precise radial velocity of an emitter. This mathematical shift is an inescapable consequence of the expansion of space and relative momentum. The calculation provides absolute, objective proof of cosmic kinematics, devoid of any observer-dependent illusions.

A spectral line is a fixed fingerprint — hydrogen always emits at 656.28 nm when at rest. Measure where you actually see that line: if it drifts to a longer (redder) wavelength the source is receding; a shorter (bluer) one means it approaches. The redshift z is simply the fractional stretch. Seeing H-alpha at 660 nm instead of 656.28 nm gives z ≈ 0.0057, a recession of roughly 1700 km/s.

Load the quasar preset: Lyman-alpha shifts from 121.567 nm to 486.268 nm, so z = 3 and the line quadruples (1 + z = 4). The naive v = zc would claim three times light speed — impossible. The relativistic formula β = ((1+z)²−1)/((1+z)²+1) instead gives 15/17 ≈ 0.88, safely below c. No matter how large z grows, β never reaches 1.