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

A star emits all frequencies of visible light, so you should see a pure spectrum. Elements within the star will absorb certain frequencies, so you actually see a spectrum with lots of black dots in it.

We can measure how far away the star is, based on parallax or proximity to standard candles (objects that we know have a certain brightness).

Only distant galaxies, where individual stars are too small to be seen, have a significant redshift.

<cough the wavelength *increases* with red shift. The *frequency* reduces.>