Why did astronomers suspect an eighth planet beyond Uranus? How did they determine where to look for it? Construct the correct explanation. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

Brightness - mass - orbit - position - Kepler's third law - value - Law of Gravity

Observation of Uranus showed small but significant discrepancy between its predicted and its actual , which could mean that another object perturbed its motion.
In the mid-1800s, astronomers used the to predict where a planet would have to be.