Why is Pluto no longer considered a planet?

Why is Pluto no longer considered a planet?

• A. It has too much junk in its orbit
• B. It is too far away
• C. It is not large enough
• D. It orbits a dwarf star

Answer: (A)

The key idea is how a planet is defined: a body must not only orbit the Sun and be roughly round, but it must have cleared its orbital neighborhood of other debris. Pluto sits in the Kuiper Belt, a region filled with many small objects, and it hasn’t become the gravitationally dominant body in that zone. Because of that, it’s classified as a dwarf planet rather than a full planet. Saying it has “too much junk in its orbit” is a natural way to express this idea of not clearing its neighborhood.

The other statements miss the real criterion. Distance isn’t the reason—there are planets far out in the solar system. Size isn’t the deciding factor—some smaller bodies are still planets if they’ve cleared their orbits. And Pluto does not orbit a dwarf star; it orbits the Sun, a normal main-sequence star.