Although a number of the larger members of this group were initially described as planets , in 2006 the International Astronomical Union reclassified Pluto and its largest neighbours as dwarf planets , leaving Neptune the farthest known planet in the Solar System .
Although a number of the larger members of this group were initially described as planets , in 2006 the International Astronomical Union reclassified Pluto and its largest neighbours as dwarf planets , leaving only eight planets in the Solar System .