How do we know that the light coming off from distant planets is as a result of red shift or the properties of the elements prevalent on the plant?

Question

My understanding is that when an object moves away from you it increases the wavelength of the light presenting with a colour that is on the red side of the colourscale. Scientists also are able to determine what elements are present on planets based on the light it emits. How can they tell the difference?

I’m sorry for possibly using the incorrect terminology! Thanks in advance folks!

Edited the post because previously I had suggested that shorter wavelengths tended to the red side when in fact longer wavelengths tended to the red side of the colour spectrum.

In: 17

Answer 1

Basically different elements emit(or absorb) a specific pattern of wavelengths, this is due to the possible energy levels of electrons. So every element basically has a signature that we can look for, and if that signal is shifted towards red we can calculate very precisely how much the light has been redshifted, and the signal can also tell us about the chemical/atomic make up of whatever we are looking at.