Qu'est-ce que Redshift Calculator ?
Calculate cosmological redshift from rest and observed wavelengths, or convert between redshift and recession velocity with this free redshift calculator. Get Hubble distance, scale factor, and relativistic velocity. Includes H-alpha, Lyman-alpha, and quasar presets. Runs entirely in your browser with no signup.
Comment utiliser Redshift Calculator
- Choose Wavelength, Redshift, or Velocity mode.
- Enter rest and observed wavelengths, redshift z, or recession velocity.
- Set the Hubble constant H₀ (default 70 km/s/Mpc) for distance estimates.
- Click Calculate to get z, velocity, scale factor, and Hubble distance.
- Copy results and step-by-step formulas.
Cas d'usage courants
- Computing redshift from a shifted H-alpha spectral line
- Finding recession velocity for a galaxy with z = 0.5
- Estimating Hubble distance for a quasar at z = 6
Questions fréquentes
- How is redshift calculated from wavelength?
- z = (λ_observed − λ_rest) / λ_rest. A positive z means the source is redshifted (receding); a negative z is a blueshift (approaching).
- What is the relativistic velocity formula?
- For radial motion, v = c × ((1+z)² − 1) / ((1+z)² + 1). At low z this approximates the classical v ≈ cz.
- What is Hubble distance?
- Using Hubble's law v ≈ H₀d, distance d ≈ cz/H₀. With H₀ = 70 km/s/Mpc and z = 0.1, d ≈ 428 Mpc. This is a low-redshift approximation.
- What does the scale factor mean?
- The cosmological scale factor a = 1/(1+z). A redshift of z = 1 means the universe was half its current size when the light was emitted.
