How does Romeo compare Juliet to the sun, moon, and stars?

In Act 2, at the beginning of the balcony scene, Romeo overflows with the first raptures of love for Juliet. His initial thought as the sun rises and he sees her in the window is that she is the sun. He accuses the moon of being pale (sick) and green with envy at how much more beautiful the "sun" of Juliet is. He connects the moon with virginity, a classical way of understanding it, calling it the "vestal" [virginal] moon and saying it would be less of a fool if it would cast off the "livery" or clothing of the virgin. 

 Romeo, still in raptures, likens Juliet's eyes to the stars in the heavens. He says that her eyes are so beautiful that "two of the fairest stars" in heaven, off to do business, have asked her eyes to "twinkle" in their place until they return. Juliet's cheeks, says Romeo, are so bright they put those stars to shame. In fact, returning to her eyes again, Romeo says they shine so brightly they would light up the night sky like the sun, so "that birds would sing and think is was not night." Juliet is incredibly beautiful to Romeo, a sun in the sky, brighter than the stars and the moon.

This hyperbolic or over-the-top language represents how head-over-heels in love Romeo is with Juliet and foreshadows the great lengths he will go to in order to be with her.