Astrophysics (index)


(change to longer wavelengths due to Doppler affects)

Redshift is a lengthening of Wavelengths, e.g., of Spectral Lines, due to Doppler effects of radial motion of the radiation source away from the observer. Given the expansion of the universe, it is used as a measure of distance and time, and a redshift due to this is called a Cosmological Redshift.

Smaller redshifts and Blue Shifts (for the analogous shortening of the wavelength from sources moving toward the observer) are also measured to determine Radial Velocity in studies of Peculiar Velocity and of objects orbiting stars such as Extra Solar Planets and Binary Star companions. Measurements using specially developed Spectrographs can determine radial velocities and radial velocity differences as small as 1 meter per second.

For radial motion, redshift z is:

              1 + v/c
1 + z = sqrt( ——————— )
              1 - v/c


     observed wavelength - Rest Wavelength
z =  —————————————————————————————————————
              rest wavelength

Traverse motion also causes a redshift with a different formula. Gravity also affects Electromagnetic Radiation and produces a redshift.

When a body's redshift is determined, a distance estimate can be calculated using its redshift and the Hubble Constant (70 kmps/Mpc). Below are some calculated values. "Linear" was calculated using a simple linear approximation (workable for z less than 0.1) and "Relativistic" takes Special Relativity into account (the above formula) and is suitable for all redshifts. "Giga Years" is how far in the past we're viewing the body and is also its distance in billions of light-years.

zMpc and GYearsMpc and GYears
0.0143Mpc 0.1GY43Mpc 0.1GY
0.0286Mpc 0.3GY85Mpc 0.3GY
0.03129Mpc 0.4GY127Mpc 0.4GY
0.04171Mpc 0.6GY168Mpc 0.5GY
0.05214Mpc 0.7GY209Mpc 0.7GY
0.06257Mpc 0.8GY249Mpc 0.8GY
0.07300Mpc 1.0GY290Mpc 0.9GY
0.08343Mpc 1.1GY329Mpc 1.1GY
0.09386Mpc 1.3GY368Mpc 1.2GY
0.1429Mpc 1.4GY407Mpc 1.3GY
0.2857Mpc 2.8GY773Mpc 2.5GY
0.31286Mpc 4.2GY1099Mpc 3.6GY
0.41714Mpc 5.6GY1390Mpc 4.5GY
0.52143Mpc 7.0GY1648Mpc 5.4GY
0.62571Mpc 8.4GY1878Mpc 6.1GY
0.73000Mpc 9.8GY2082Mpc 6.8GY
0.83429Mpc 11.2GY2264Mpc 7.4GY
0.93857Mpc 12.6GY2426Mpc 7.9GY
14286Mpc 14.0GY2571Mpc 8.4GY
1.56429Mpc 21.0GY3103Mpc 10.1GY
28571Mpc 28.0GY3429Mpc 11.2GY
312857Mpc 41.9GY3782Mpc 12.3GY
417143Mpc 55.9GY3956Mpc 12.9GY
521429Mpc 69.9GY4054Mpc 13.2GY
625714Mpc 83.9GY4114Mpc 13.4GY
730000Mpc 97.8GY4154Mpc 13.5GY
834286Mpc 111.8GY4181Mpc 13.6GY
938571Mpc 125.8GY4201Mpc 13.7GY
1042857Mpc 139.8GY4215Mpc 13.7GY
1147143Mpc 153.8GY4227Mpc 13.8GY
1251429Mpc 167.7GY4235Mpc 13.8GY
1355714Mpc 181.7GY4242Mpc 13.8GY
1460000Mpc 195.7GY4248Mpc 13.9GY
1564286Mpc 209.7GY4252Mpc 13.9GY
100428571Mpc 1397.8GY4285Mpc 14.0GY


Referenced by:
Alcock-Paczyński Effect
Astronomical Quantities
Balmer Series
Balmer-Break Galaxy (BBG)
Brightest Cluster Galaxy (BCG)
Baryon Oscillation Spectroscopic Survey (BOSS)
Calán/Tololo Survey
Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS)
Carbon (C)
Cepheid Variable
Canadian Hydrogen Intensity Mapping Experiment (CHIME)
Cosmic Infrared Background (CIB)
Cluster Radius
Cosmic Microwave Background (CMB)
Carbon Monoxide (CO)
Carbon Monoxide Mapping Array (COMA)
Cosmic Distance Ladder
Cosmological Time Dilation
Cosmological Zoom Simulation
Cosmic Evolution Survey (COSMOS)
Critical Density (ρc)
Dark Age
Dark Energy Spectroscopic Instrument (DESI)
Extended Groth Strip (EGS)
Emission Line Galaxy (ELG)
Emission Line
Epoch of Reionization (EOR)
Epoch of Galaxy Formation
Faber-Jackson Relation
Faint Infrared Grism Survey (FIGS)
First Galaxies
Galaxy Cluster (CL)
Galaxy Merger
Galaxy Power Spectrum
Gas Fraction Estimation
Gemini Observatory
Giant Metrewave Radio Telescope (GMRT)
Gravitational Redshift
Great Attractor
Great Debate
Gunn-Peterson Trough
Galaxy Zoo 2 (GZ2)
Hercules-Corona Borealis Great Wall (Her-CrB GW)
Herschel Redshift Survey (HeRS)
Hubble Constant (H0)
Hubble Ultra-Deep Field (HUDF)
K Correction
Lyman-Alpha Emitter (LAE)
Lambda-CDM model (ΛCDM)
Lyman-Break Galaxy (LBG)
Line Broadening
Large Millimeter Telescope (LMT)
Low-Frequency Array (LOFAR)
Luminous Red Galaxy (LRG)
Luminosity Function (LF)
Lyman-Alpha Forest
Molecular Deep Field
Murchison Widefield Array (MWA)
Origins Space Telescope (OST)
Palomar Four-Filter Survey (PC)
Peak Star-Formation Epoch
Photometric Redshift
Quasar (QSO)
Redshift Space
Rest Wavelength
Supernova Cosmology Project (SCP)
Sloan Digital Sky Survey (SDSS)
Star Formation History (SFH)
Star Formation Rate (SFR)
Spitzer HETDEX Exploratory Large Area Survey (SHELA)
Submillimeter Galaxy (SMG)
Supernova Legacy Survey (SNLS)
Spectral Line
Sachs-Wolfe Effect (SWE)
3C 273
3C 295
3C 48
Time Dilation
Tomographic Ionized-Carbon Mapping Experiment (TIME)
21cm Experiment
21cm Line
2dF Galaxy Redshift Survey (2dFGRS)
Ultraluminous Infrared Galaxy (ULIRG)
USS Sources