Why Pluto Isn't A Planet Anymore

Amaryllis Place — Thu, 07 May 2009 20:23:00 GMT

The Kuiper Belt is a region in space beyond the orbits of the planets in our solar system, similar to the asteroid belt but 20 times wider, where there are many small bodies. With the advances in our telescopes, more objects have been found similar in composition to Pluto but larger. The question of what to classify them has arose. To help answer this, the International Astronomical Union (IAU) formalized the definition of a "planet" in 2006. To qualify as a planet, a body must meet three requirements:

It needs to be in orbit around the Sun.
It needs to have enough gravity to pull itself into a spherical shape.
It needs to have cleared the neighborhood of its orbit.

Pluto fails to meet the third requirement. Any object not meeting the third requirement is called a dwarf planet. Pluto, Ceres, and Eris became the first three members of the dwarf planet classification, and many others are expected to follow.

I was a little sad at Pluto's demotion to a dwarf planet. However, I understand the need to be more precise. Our knowledge base changes as we learn more things about this world. After all, there was big upheaval over the Earth not being flat and not at the center of the universe and yet we managed to get over that eventually.

Gimme Some Space : Pluto

Why Pluto Isn't A Planet Anymore