The orbit of Neptune limits Uranus. Gravity pulls Uranus toward the Sun. Electromagnetic energy pulls on Uranus. Other planets have the same mass as Uranus.
I gave my students this multiple choice question: Uranus is one of the outer planets of the solar system. The average distance of Uranus from the Sun is 2.87 billion kilometers. Which best explains why Uranus revolves in its orbit instead of moving out into space?

Only one answer is correct among these 4 choices:
- The orbit of Neptune limits Uranus.
- Gravity pulls Uranus toward the Sun.
- Electromagnetic energy pulls on Uranus.
- Other planets have the same mass as Uranus.

Could you tell me which one is correct?

Gravity pulls Uranus toward the Sun.