Even our solar system is vast, where do we get the proof of our spiral galaxy?
In: Planetary Science
From measuring the different wavelength of light coming from a star (or lack of) we can determine what type of star it is. Different stars emit a different type of light and can be vastly different in size. We can also determine roughly what direction the star is moving in depending on how red-shifted or blue shifted the light is.
Using this information along with the “size” it appears in our sky/telescopes we can map out how far each star is. We do that for all the stars and over time we find that there are some areas that are denser with stars and some areas less dense, we plot all that out and it shows the shape of our galaxy. As we keep measuring more and more stars it then fine tunes our models.
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