Pluto
Pluto was discovered in 1930. It was known as the most distant planet from the Sun until August 24, 2006 when the International Astronomical Union (IAU) formally downgraded Pluto to a dwarf planet. Pluto takes 248 years to orbit the Sun. At this scale it is about the size of a pea. Info from NASA.gov
Pluto, (PLOO toh), is a dwarf planet that orbits far from the Sun. It shares the region of its orbit, known as the Kuiper belt, with a collection of similar icy bodies called Kuiper belt objects (KBO’s). From its discovery in 1930, people widely considered Pluto to be the ninth planet of our solar system. However, because of its small size and irregular orbit, many astronomers questioned whether Pluto should be grouped with worlds like Earth and Jupiter. Pluto seemed to share more similarities with KBO’s. In 2006, this debate led the International Astronomical Union, the recognized authority in naming heavenly objects, to formally classify Pluto as a dwarf planet. Pluto cannot be seen without a telescope. [+]Read more at NASA.govSun | Mercury | Venus | Earth | Mars | Jupiter | Saturn | Uranus | Neptune | Pluto