The mass of the Sun is 2 × 1030 kg, and the distance between Neptune and the Sun is 30 AU. What is the orbital period of Neptune in Earth years?

For planets orbiting the Sun, Kepler’s third law in Earth units is P² = a³, where P is the period in Earth years and a is the distance in AU. With a = 30, P = √(30³) = √27,000 ≈ 164 years. Therefore, the correct choice is 164 Earth years.

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