UNLOCKED SECRETS
Throughout the years of studying space, Pluto was always known as the smallest planet within our solar system. However, in 2006 the International Astronomical Union (IAU) proposed the definition of a planet as an object that orbits around the sun, large enough to have become round because of its own gravity, and with enough gravity to clear debris from its orbit.
By this definition, the IAU does not consider Pluto to be a planet, as it in fact does not have enough gravity to clear debris from its orbit. It is only regarded as a dwarf planet. Astronomers have since discovered more dwarf planets in our solar system, now six in total. With the discovery of even more of these smaller round celestial bodies in our solar system, some astronomers are now proposing for a new classification system for dwarf planets.
Under the current classification, dwarf planet should have a minimum radius of 420 km (260 miles). However, astronomers in Australia are now calling for the minimum size to be reduced to 200 km (124 miles) for icy bodies and 300 km (186 miles) for rocky bodies. If that is the case, roughly 50 small rocky and icy bodies in our solar system's Kuiper Belt will become dwarf planets, with Pluto being the second biggest amongst them.