Pre-Copernican
7 Classical Planets
16th century
Copernican Revolution
Mercury, Venus, Earth, Mars, Jupiter and Saturn considered planets (maybe more)
1781
Uranus discovered (named 7th Planet)
1801
Ceres Mistaken for 8th Planet
1802
2 Pallas discovered (considered planet)
1846
Neptune discovered (named 13th Planet [citation needed])
1851
Ceres recategorized as Asteroid
Neptune renamed to 8th Planet
1867
2 Pallas removed as planet
Juno removed as planet
Vesta removed as planet
5 Astraea removed as planet
2006
Eris discovered
Pluto removed as planet