In the 1990s

In the 1990s, astronomers began to find objects in the same region of space as Pluto (now known as the Kuiper belt), and some even farther away.[17] Many of these shared some of the key orbital characteristics of Pluto, and Pluto started being seen as the largest member of a new class of objects, plutinos. This led some astronomers to stop referring to Pluto as a planet. Several terms including minor planet, subplanet, and planetoid started to be used for the bodies now known as dwarf planets.[18][19] By 2005, three other bodies comparable to Pluto in terms of size and orbit (Quaoar, Sedna, and Eris) had been reported in the scientific literature.[20] It became clear that either they would also have to be classified as planets, or Pluto would have to be reclassified.[21] Astronomers were also confident that more objects as large as Pluto would be discovered, and the number of planets would start growing quickly if Pluto were to remain a planet.[22]


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