Redshift converter
Convert redshift z into a recession speed and a rough distance, and see how far a spectral line moves.
That's 4.3× as distant as the Coma cluster, while the nearest quasar is 1.58× further. Light from it arrives about 10% longer in wavelength.
What it means
How far is that?
Distances use a simple Hubble law at 70 km/s per Mpc, which is only a good guide for small z. Beyond about z = 0.1 the real answer depends on the expansion history.
Every unit
Your redshift in every unit
Learn
Three things worth knowing
-
z = stretch in wavelength
Observed wavelength ÷ emitted wavelength = 1 + z. So z = 1 means the light arrives at double the wavelength it left with.
-
Hubble read the shift as distance
In 1929 he showed that the further a galaxy is, the more its light is shifted. That single graph turned redshift into the yardstick of cosmology.
-
Big z is not superluminal
A naive z × c gives faster than light above z = 1. The relativistic version never does, because space is stretching rather than anything travelling through it.
Shortcuts
Popular redshift conversions
Background
About redshift
As the universe expands, light stretches on the way to us. z is how much: a z of 0.1 means every wavelength arrives 10% longer than it left. Hydrogen’s 656 nm line comes in at 722 nm.
Small redshifts read as a speed; large ones are not really speeds at all, but stretched space, which is why nothing passes the speed of light however big z gets.