IAU definition of planet

Quick Facts: Who was IAU definition of planet?

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IAU definition of planet

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The IAU's 2006 definition: A planet orbits the Sun, has mass for round shape, and cleared its neighborhood.

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2Day Chrono-Wiki & Primary Historical Archives

Origins & Early Life

In August 2006, the International Astronomical Union (IAU) adopted a new definition of the term planet, which stated that, in the Solar System, a planet is a celestial body that: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit. A non-satellite body fulfilling only the first two of these criteria (such as Pluto, which had hitherto been considered a planet) is classified as a dwarf planet and not a planet. A non-satellite body fulfilling only the first criterion is termed a small Solar System body (SSSB).

Career & Major Achievements

An alternate proposal included dwarf planets as a subcategory of planets, but IAU members voted against this proposal. The decision was a controversial one, and has drawn both support and criticism from astronomers.

Enduring Legacy & Impact

The IAU has stated that there are eight known planets in the Solar System. It has been argued that the definition is problematic because it depends on the location of the body: if a Mars-sized body were discovered in the inner Oort cloud, it would not have enough mass to clear out a neighbourhood that size and meet criterion 3.

Chronological Milestones & Life Events

1. 2006: 2006 Milestone — In August 2006, the International Astronomical Union (IAU) adopted a new definition of the term planet, which stated that, in the Solar System, a planet is a celestial body that: is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit.

Notable Quotes by IAU definition of planet

“The final definition, as passed on 24 August 2006 under the Resolution 5A of the 26th General Assembly, is: [criteria listed]” (2006)

Historical Fact-Check Quiz: IAU definition of planet

True or False: “The IAU's 2006 definition requires a planet to have cleared the neighborhood around its orbit.”

Answer (TRUE ⭕): This third criterion, 'clearing the neighborhood,' is one of the three necessary conditions established by the IAU in 2006 for a celestial body to be classified as a planet.

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