this post was submitted on 27 Sep 2023
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Stars can appear red or blue depending on the direction they are traveling. It has to do with the frequency of light they put out. As they move away the frequency gets lower, which we interpret as red. As they get closer the frequency gets faster which we interpret as blue.
I am not an astronomer or even a casual stargazer. I took a single class in Astronomy in college and this was a neat fact I picked up. I remember next to nothing else from the class other than the fact that you can fit every planet between the earth and moon.
That isn't really observable to our naked eye though, that's Doppler shift and is the same thing that makes a sound change pit h if it's coming towards you or away from you (think of a siren as a cop car passes you). The Doppler shift, or redshift of stars and other celestial objects is how the expansion of the universe can be observed and measured.
This is all correct and is commonly known as redshift or blueshift. Itβs the same idea as when a car or train passes by and you hear the pitch get higher as it approaches you, and then lower as it leaves you.
To add to it though, stars themselves (regardless of our perspectives on them) do come in different colors. Betelgeuse is an easy star to find in the night sky that has a distinctly redder color compared to most stars. Itβs the left armpit star in the constellation Orion.
Stars have different colors based on many factors like their composition and how hot they burn.
I don't think redshift applies to stars, as all the stars we can see are in the milky way and not moving away from us, not sure of there's any galaxies you can see with the naked eye
It does apply, technically, but yeah the effect is too small to see with the naked eye
A few nearby galaxies are visible, most notably Andromeda, but still redshift isn't naked eye visible for these