Why do some stars in the night sky appear red?
Either because they are at the red spectrum (like red giants) or because Mr. Doppler said so 😉 Mr. Doppler (Christian Doppler) said that The Doppler effect is the change in frequency and wavelength of a wave for an observer moving relative to the source of the waves. This was more commonly related to the way sounds modulate (change) as say a fire truck approaches and when it leaves. However it also applies to light. Stars that are moving away from our location space relative in the galaxy take on a red tinge. Stars that are on the approach to our location relative in the galaxy take on a blue tinge. This also applies to galaxies – those moving away from our galaxy are reddish, those approaching are bluish. The Redder the color or the bluer the faster stars (or galaxies) are moving in relation to each other.
