Final answer:
The Sun's gravitational pull does not have a specific limit and extends indefinitely into space, weakening with distance but never reaching zero. The Sun's influence is observed as far as the outer solar system and contributes to the gravitational pull of the Milky Way Galaxy.
Step-by-step explanation:
The gravitational pull of the Sun extends far beyond the planets in our solar system and is not limited to a specific distance. Newton's law of gravitation implies that gravity, while it weakens with distance, never actually becomes zero. This means that the Sun's gravitational influence can be felt indefinitely far into space, decreasing in strength as one moves away from it.
The Sun's pull is stronger at Mercury than at Pluto, but it can be detected far beyond Pluto. Astronomers observe its effects on the orbits of numerous icy bodies in the outer solar system. Additionally, the Sun's gravity, combined with that of billions of other stars, contributes to the overall gravitational field of the Milky Way Galaxy, affecting the motion of nearby galaxies. Therefore, none of the options provided (five million kilometers, one billion kilometers, five billion kilometers, or ten billion kilometers) accurately reflects the true extent of the Sun's gravitational field, which can be conceptualized as infinite for all practical purposes.