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

1. A beam of light leaves a star.
2. It arrives at our measurement device.
3. We can measure that beam’s wavelength to determine how far away it originated.

A) Elements in the star’s corona absorb some of the light as it leaves the star.
B) Those absorptions leave gaps in the beam’s spectrum.
C) We can identify the elements in the corona based on the position of those gaps in the beam’s spectrum.