What happen to the spectrum of a star moving toward the earth away from the earth?

Answer 1

If a star is moving towards Earth. The light is seen as 'blue shifted'. As we look at our sun, on the colour spectrum, black lines appear. When looking at distant stars, we can tell if they are moving away from us (Red shift) or getting closer to us (Blue shift). This is because the black lines shift to the red or blue end of the spectrum depending on which direction the star is travelling.

Answer 2

Moving toward the earth, it's light spectrum would be shifted to the blue range, and moving away, it's spectrum would be shifted to the red part of the spectrum. In reality, all observed shift is red shift, as everything in the universe is moving away from everything else, as Einstein explained in Relativity.

Answer 3

The light waves will be squashed together more, so the apparent wavelength will be shorter than the actual wavelength (higher frequency). So the observed light will be shifted from the actual light emitted and this will be relative to the speed (so the speed can be worked out). A star giving off a reddish colour will be seen to shift towards the blue end of the spectrum, if coming towards us.