The decision to reinstate Pluto as a planet is not a recent topic of debate, however. There has been much argument over the classification of a planet since the ruling was made by the IAU.

Bring up the former planet Pluto in conversation and you’re guaranteed to be met with a strong opinion. In one camp are those ...

The debate over Pluto’s status highlights the evolving nature of scientific classification. Definitions should reflect our growing understanding rather than arbitrary criteria.

But why isn't Pluto considered a planet anymore? It starts with the definition of a planet — or lack thereof. Before 2006, there weren't strict criteria for a planet.

While Planet X was estimated to be about six times more massive than Earth, Pluto’s mass is only 20% that of the Moon, itself 1% of the Earth’s mass. Pluto is much too small to gravitationally ...

At this moment, Pluto is still classified as a dwarf planet. Despite ongoing debate and public support for its reinstatement, the International Astronomical Union has not changed its 2006 decision.

Pluto had been considered our solar system’s ninth planet since its discovery in 1930. But in 1992, astronomers discovered Pluto’s small, icy neighbors in what has become known as the Kuiper Belt.

In 2006, the IAU famously dropped Pluto from the pantheon of planets because it did not meet the union’s criteria. As stated on the union’s website, a planet in the solar system: ...

Though Pluto has formally been considered a dwarf planet for almost two decades, it still has many lessons left for planetary scientists — including hints about how the solar system formed.

Pluto may have lost its status as a full-fledged planet in 2006, but that doesn't mean it's a joke of a world this April Fools' Day and the folks behind Pluto TV want to make that clear.

“For that reason alone, Pluto’s status as a full-fledged planet should be kept.” Tombaugh came to NMSU in 1955 and developed a world-class astronomy research program.

Pluto, therefore, is not the gravitationally dominant object in its neighborhood — and thus, not a planet, according to the new definition.