The Classification of Pluto

Pluto

• Pluto is located beyond Neptune, the planet furthest away from the sun, in a region called the Kuiper Belt. Within the Kuiper Belt region there are thousands of small icy worlds, formed early in the history of the solar system. Pluto itself is two-thirds the diameter of the Earth's moon, and probably has a rocky core, surrounded by a mantle of water ice, according to NASA scientists. It takes Pluto 248 years to orbit the sun.

Classification of Pluto - Dwarf Planet

• In 2006, Pluto was stripped of its planet classification and redefined as a dwarf planet. This decision was made by a committee of the International Astronomical Union (IAU), as detailed by Richard Gray, science correspondent for "The Telegraph." According to Dr. Emily Baldwin in "Astronomy Now," this decision was made following numerous discoveries of Pluto-like bodies in the far reaches of the solar system, some of which where even larger than Pluto. If all these were to be classed as planets it would take the solar system's planet inventory to more than 50 planets, thus a reclassification was necessary.

Classification of Pluto - Plutoid

• In 2008, the IAU introduced the term 'plutoid' to describe "celestial bodies in orbit around the sun at a distance greater than that of Neptune, that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a near-spherical shape and that have not cleared the neighborhood around their orbit of debris." Furthermore, according to Baldwin, the new body must have a magnitude brighter than +1 to be considered a plutoid. Thus, Pluto is now classed as a plutoid.

Controversy

• When Pluto was first reclassified as a dwarf planet in 2006, many scientists opposed the idea. Many disagreed with abandoning a planet that had been a feature of the solar system for around 70 years. Moreover, teachers and textbook writers were left with the task of revising the view of the solar system.