# How do someone calculate the wavelength of a receding object in space? [duplicate]

Is it possible to calculate the original wavelength of a star, say, which is subjected to cosmological redshift? if yes, how?

Looking at the answers I think I need to edit it to be more specific. Suppose I'm observing a galaxy, I observe it's spectrum. From the doppler shift I indeed can calculate its velocity. Now say, z>6 then you can see it's not any sort of normal redshift, rather its the cosmological redshift.

Now my question is, from z value I'll get the a(expansion factor ), it's distance and hence how old the radiation is, but can I calculate its original wavelength and hence its temperature.

how do I calculate these??