Milky Way rotates faster and as heavy as Andromeda

Painius I get your angle analysis and it fits. So would a star moving
away from us with less light intensity(already shinning closer to
red(kind of pink white) Also mass density of star.as it radiates white
light but its great gravity changes photons to be longer and longer
lengths in their great journey to hit our eyes. TreBert PS Wave
lengths of photons tell us a lot ,but to measure each photon wave
accurately is ????