Why did William Herschel have to observe Uranus on more than one night before he could be sure it was a planet and not a star?
A)He had to see if it showed a full range of phases from new to full
B)He had to see if it moved among the stars from night to night
C)He had to see if it had satellites
D)He had to see if it varied in brightness from night to night

Question

Quizplus · Accepted Answer

William Herschel had to observe Uranus on more than one night to confirm it was a planet and not a star because he had to see if it moved among the stars from night to night. Planets move relative to the background stars, while stars appear fixed in position. By observing Uranus over a few nights, Herschel could track its movement and confirm it was a planet.

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