Why do astronomers think that the milky way is a spiral galaxy?

1) When you look toward the Galactic Center with your eye, you see a long, thin strip. This suggests a disk seen edge-on, rather than a ellipsoid or another shape. We can also detect the bulge at the center. Since we see spiral galaxies which are disks with central bulges, this is a bit of a top.

think its the third option

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нσρє ι ¢συℓ∂ нєℓρ.