Celestial Objects
Dwarf Planet
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The largest object in the asteroid belt between Mars and Jupiter, discovered on 1 January 1801 by Giuseppe Piazzi and originally classified as a planet, then as an asteroid once similar bodies were found nearby. The International Astronomical Union's 2006 definition of planet, which requires a body to have cleared its orbital neighborhood, reclassified Ceres as a dwarf planet alongside Pluto. Little was known about its surface until NASA's robotic Dawn spacecraft entered orbit around it in 2015, the first spacecraft ever to orbit a dwarf planet.
Facts
Disputed
Object TypeDwarf planet (IAU classification, 2006, asteroid belt); planet (1801 classification) 1 Classified a planet at discovery in 1801, then an asteroid once similar bodies were found nearby, then a dwarf planet under the IAU's 2006 dynamical definition; a minority of planetary scientists, including New Horizons principal investigator Alan Stern, reject that dynamical definition in favor of a geophysical one that would restore Ceres to full planet status. See the recorded dissent on this fact. Diameter (km) Orbital Distance2.77 AU (about 414 million km from the Sun) 1 Discovery Year Cross-Tradition Connections
Associated With
Pluto, Celestial Objects Why this is disputed. Both bodies were reclassified as dwarf planets under the IAU's 2006 dynamical definition of planet, a classification a minority of planetary scientists dispute in favor of a geophysical definition; see the recorded dissent on Ceres's object-type.
Orbits
Sun, Celestial Objects Ceres orbits the Sun within the main asteroid belt between Mars and Jupiter.
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres dwarf planet (Wikipedia) - dwarf planet classificationQuote, Ceres dwarf planet (Wikipedia) - dwarf planet classification
Bodies that met the first proposed definition but not the second, such as Ceres, were instead classified as dwarf planets.
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres dwarf planet (Wikipedia) - discoveryQuote, Ceres dwarf planet (Wikipedia) - discovery
discovered on January 1, 1801 by Giuseppe Piazzi
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres dwarf planet (Wikipedia) - diameterQuote, Ceres dwarf planet (Wikipedia) - diameter
approximately 939 km (583.7 miles)
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres dwarf planet (Wikipedia) - object typeQuote, Ceres dwarf planet (Wikipedia) - object type
classified as dwarf planets
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres (dwarf planet), Wikipedia - physical characteristics infoboxQuote, Ceres (dwarf planet), Wikipedia - physical characteristics infobox
approximately 9.38392 x 10^20 kg
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres (dwarf planet), Wikipedia - orbital characteristics infoboxQuote, Ceres (dwarf planet), Wikipedia - orbital characteristics infobox
2.77 AU (414 million km)
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCeres (dwarf planet), Wikipedia - lead section respellingQuote, Ceres (dwarf planet), Wikipedia - lead section respelling
SEER-eez
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Pluto, Dwarf planet (Wikipedia) - Ceres and Pluto pairingQuote, Associated With: Pluto, Dwarf planet (Wikipedia) - Ceres and Pluto pairing
such as Ceres, were instead classified as dwarf planets
Dissenting Readings (1 dissenting reading)
Object Type
The IAU's 2006 dynamical definition of planet requires a body to have gravitationally cleared its orbital neighborhood, which excludes Ceres, Pluto and other dwarf planets. A minority of planetary scientists, prominently New Horizons principal investigator Alan Stern, reject this dynamical test and argue for a geophysical definition based on a body's intrinsic roundness (hydrostatic equilibrium) instead of its orbital surroundings; under that definition Ceres, Pluto and other dwarf planets would count as full planets. The IAU's definition remains the operative classification used by this atlas, but the dispute is unresolved among working planetary scientists.
A dissenting reading, from an independent laneWikipedia (space and spaceflight articles), Wikimedia Foundation
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