If Pluto were a planet what would make it so?

Answer 1

A planet has to be a certain size to become a planet. Pluto is under that size so it is not a planet. It is infact a unnaturally big peice of rock.

This is not correct. First, the planetary status of Pluto is still very much a matter of debate. Many astronomers still consider Pluto a planet in spite of the controversial demotion by four percent of the International Astronomical Union. That decision was rejected in a formal petition by hundreds of professional astronomers led by New Horizons Principal Investigator Dr. Alan Stern.

Stern and like-minded scientists favor a broader planet definition in which a planet is defined as any non-self-luminous spheroidal body orbiting a star. If an object is large enough to be pulled into a round shape by its own gravity--a characteristic of planets and not of shapeless asteroids and "big rocks," then it is a planet. When an object is large enough that its shape is determined by gravity rather than by chemical bonds, it is said to be in a state known as hydrostatic equilibrium.

So from this viewpoint, if an object is in hydrostatic equilibrium and orbits the sun (or another star), it is a planet. That most certainly qualifies Pluto.

Answer 2

Pluto used to be classified as the ninth planet in our solar system due to its orbit around the Sun and spherical shape, meeting the criteria for a planet at the time. However, in 2006, the definition of a planet was revised, and Pluto no longer met all the criteria as it shares its orbit with other objects in the Kuiper Belt.