Question

Why does IAU classify Pluto as a dwarf planet?

Answer 1

Почему IAU классифицирует Плутон как карликовую планету?

Answer 2

The International Astronomical Union (IAU) classified Pluto as a dwarf planet on August 24, 2006. This decision was made during the IAU's General Assembly in Prague, Czech Republic. The main reasons for reclassifying Pluto were:

1. Size: One of the key criteria for a celestial body to be considered a planet is that it must have "cleared its orbit," meaning it has become gravitationally dominant in its orbital zone and cleared away other debris and objects. Pluto, while relatively large compared to other objects in the Kuiper Belt (a region beyond Neptune's orbit), has not fully cleared its orbit. It shares its orbital region with other objects, which led to its reclassification as a dwarf planet.

2. Neighboring Objects: Pluto is located in the Kuiper Belt, which is populated with numerous small icy bodies. These objects are similar to Pluto in composition and size. The discovery of these objects challenged Pluto's unique status as the ninth planet in our solar system.

3. Definition of a Planet: Prior to 2006, there was no official definition of what constitutes a planet. The IAU's decision to create a clear definition for the term "planet" led to Pluto's reclassification. According to the new definition, a celestial body must meet three criteria to be classified as a planet:

   a. It must orbit the Sun. b. It must be spherical due to its self-gravity. c. It must have "cleared its orbit" as described in point 1 above.

Since Pluto did not meet the third criterion, it was reclassified as a dwarf planet.

This decision sparked some controversy and debate among scientists and the public, as Pluto had been traditionally regarded as the ninth planet in our solar system since its discovery in 1930. However, the IAU's reclassification aimed to create a more precise and scientifically consistent definition for the term "planet" and to recognize the distinct characteristics of objects in our solar system more accurately.