No man made object or probe has traveled far enough to see the milky way galaxy from a distance in profile, so how do we know what it looks like from billions of miles in a direction we've never visited?
are they just guessing at the shape/composition of our galaxy? We can see a band of the galaxy in the night sky but it's certainly not from an angle that sees the spiral from a perpendicular.
what is going on?
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How do we know the Milky Way Galaxy is a spiral galaxy?