Context:

• In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet.
• The definition agreed upon requires that an object meet three conditions to qualify as a planet:
  1. It must orbit the sun.
  2. It must be massive enough that its gravity pulls it more or less into a spherical shape.
  3. It must clear the neighborhood around its orbit.

Why was Pluto not classified as a planet?

• Since Neptune’s gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status.

About the Study

• It argued that the third piece of that definition does not match historical usage by scientists and should be revoked.
• Moons such as Saturn’s Titan and Jupiter’s Europa have been routinely called planets by planetary scientists since the time of Galileo.
• It recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape.

About The International Astronomical Union (IAU)

• IAU is an international association of professional astronomers.
• At the Ph.D. level and beyond, active in professional research and education in astronomy.
• Formed in 28^th July, 1919.
• Headquarters in Paris, France
• It acts as the internationally recognized authority for assigning designations and names to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them.
• The IAU is a member of the International Council for Science (ICSU).
• Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation.

Source:Science Daily