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Pluto and _____ are the only planets that cannot be seen from the Earth without a telescope.

Explanation
Neptune is the fourth largest planet in our solar system. Although it is called the eighth planet, Neptune is sometimes farther from the Sun than Pluto; Pluto moves inside Neptune's orbit for almost 20 years every 248 years. Pluto and Neptune are the only two planets that cannot be seen from the Earth without a telescope. Neptune is about 30 times farther from the Sun than our planet. Of the gas giant planets, Neptune is the farthest from the Sun. The other gas giant planets include Saturn, Jupiter, and Uranus.