Definition of a ‘Planet’ and Pluto |ForumIAS

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News: New Horizons’ probe 2015 discoveries and images captured of Pluto has renewed debate over definition of a ‘Planet’ and Pluto as a planet.

About Definition of a ‘Planet’ and Pluto

In 2006, the International Astronomical Union (IAU) met in Prague to decide what exactly should be called a planet.
Condition for recognition as planet: It was decided by IAU that a planet must satisfy three conditions:
- It must orbit the Sun.
- Sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
- An orbital path clear of other celestial objects.
Case of Pluto: Pluto met the first two conditions, but failed the third condition because it shares its orbital region with many other objects in the Kuiper Belt. Therefore, it was classified as a “dwarf planet in 2006.”
- A ‘dwarf planet’ is a celestial body that
  - is in orbit around the Sun,
  - has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,
  - has not cleared the neighborhood around its orbit, and
  - is not a satellite.
- It is recognized as the prototype of a new category of trans-Neptunian objects.
Present situation: The New Horizons mission, which reached Pluto in 2015, revealed that Pluto has nitrogen-ice glaciers, large mountains, a layered atmosphere, active geological features and five moons.
- - These discoveries renewed discussion about whether the existing definition adequately represents what a planet is.

About: IAU is a global organization of professional astronomers, at the PhD level and beyond who are active in professional education and research in astronomy.
Origin: It was founded in 1919.
Headquarters: Its headquarter is in Paris, France.
Objective: Its objective is to promote and safeguard the science of astronomy in all its aspects, including research, communication, education and development, through international cooperation.
Members: It has 92 member countries, with 85 being National Members. It also collaborates with scientific organizations globally.
Mandate: It is the internationally recognized authority for assigning designations to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them.