Some astronomers have questioned whether Pluto should be classified as a planet, rather than an errant moon or an asteroid.
The does not generate light; it is less massive than a star; it wanders through constellations; and it orbits the Sun, just like the other planets.
Pluto’s orbit, however, is decidedly peculiar.
Pluto’s distance from the Sun ranges from 4,436,824,613 km to 7,375,927,931 km depending on its orbital position.
All planets “wander” through constellations, which shows that they are not fixed in one place like stars are; because of Pluto’s orbital inclination, however, it travels through constellations that no other planet visits.
Pluto’s orbit crosses another planet’s path; no other planet does that.
One of the definitions of a planet is that it appears as a disk, not a point of light, in the sky.
Not even the most powerful telescopes on Earth were able to show Pluto as a disk until 1985, when Pluto’s moon eclipsed the planet.
This provided astronomers in Hawaii with the data necessary to map Pluto’s surface features.
Pluto, while irregular, meets the minimum requirements for a planet, but some believe it is really a planetesimal from the Kuiper Belt, or an escaped moon from Neptune.
Since 2006, Pluto has been officially classified as a dwarf planet.