Question

astronomers inferred the existence of which planet using newton's law of universal gravitation

Answer 1

Law of universal gravitation helped in determining the presence and orbit of Neptune.
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Answer 2

The answer is Neptune.

Astronomers inferred the existence of Neptune using Newton’s law of universal gravitation. The presence of this planet was inferred with the help of mathematical calculations that relied on Newton’s gravitation law. This law actually helped in observing the planet Neptune’s presence near the location it was predicted to be in.

Soon after Uranus had completed its first full orbit, some irregularities were noticed that could not be described by Newton’s law of gravitation. However, they could be accounted for if it could be considered that there was the possibility of gravity of another planet still farther way from the sun than Uranus that disturbed its path around the sun.