Tuesday, April 27, 2010

Solar System bodies formerly considered to be planets:

Body (current classification) Notes
Star Dwarf planet Asteroid Moon
Sun

The Moon Classified as planets in antiquity, in accordance with the definition then used.



Io, Europa, Ganymede, and Callisto The four largest moons of Jupiter, known as the Galilean moons after their discoverer Galileo Galilei. He referred to them as the "Medicean Planets" in honor of his patron, the Medici family.



Titan,[b] Iapetus,[c] Rhea,[c] Tethys,[d] and Dione[d] Five of Saturn's larger moons, discovered by Christiaan Huygens and Giovanni Domenico Cassini.

Ceres[e] Pallas, Juno, and Vesta
The first known asteroids, from their discoveries between 1801 and 1807 until their reclassification as asteroids during the 1850s.[52]

Ceres has subsequently been classified as a dwarf planet in 2006.



Astrea, Hebe, Iris, Flora, Metis, Hygeia, Parthenope, Victoria, Egeria, Irene, Eunomia
More asteroids, discovered between 1845 and 1851. The rapidly expanding list of planets prompted their reclassification as asteroids by astronomers, and this was widely accepted by 1854.[53]

Pluto[f]

The first known Trans-Neptunian object (i.e. minor planet with a semi-major axis beyond Neptune). In 2006, Pluto was reclassified as a dwarf planet.

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