What aspect of the Milky Way structure did Galileo *not* confirm with his 1610 observations?

Answer

The galaxy's spiral arms or its true extent

While he saw the integrated light of hundreds of thousands of stars previously merged into a smudge, he did not see the galaxy's spiral arms or understand its full extent, which required later technological advances.

What aspect of the Milky Way structure did Galileo *not* confirm with his 1610 observations?
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