What Is a Minor Planet?

A minor planet is any celestial object that rotates around the sun and is not classified as a traditional planet or a comet. Various categories of minor planets exist, including asteroids, trojans, and centaurs. The designation of dwarf planets was created in 2006, when many of the minor planets were placed into this category. Other astronomical objects that are classified as modern planets include trans-Neptunian objects and Kuiper belt objects.

More than 500 million minor planets exist in the universe, and more are discovered almost on a daily basis. In 1801, Ceres was the first minor planet to be discovered. It has since been classified as a dwarf planet, as has Pluto and a large number of the other minor planets. The International Astronomical Union (IAU) re-categorized many of the comets and minor planets in 2006, renaming a number of these as dwarf planets and small solar system bodies. While each is categorized according to specific shape, orbital and gravity standards, all are generally referred to as minor planets.

In 2006, Pluto, classified as a planet since its discovery in 1930, was demoted to a minor planet. This reclassification came about after the discovery of Eris in 2005. Initially, Eris was referred to as the 10th planet, though it is larger in diameter than Pluto. This discovery led the IAU to reevaluate the definition and required new standards for a celestial body to be classified as a planet. Under the new standards, Pluto and Eris joined Haume, Makemate, and Ceres to be classified as dwarf planets.

Special naming procedures have been set in place for minor planets. For example, trans-Neptunian objects are all named after underworld spirits, trojans after Trojan War heroes, and centaurs after mythological centaurs. Name assignment is an extremely detailed process that may take decades to complete. Only the discoverer of a minor planet has the opportunity to suggest names to the Committee for Small Body Nomenclature.

Once specific and detailed requirements have been met, names may be set forth before the naming committee. This committee is comprised of 15 professional astronomers from various locations throughout the world. Proposed names cannot be similar to any existing planetary satellite or minor planet, they must be no longer than 16 characters in length, and be pronounceable. It is preferred that the proposed name be comprised of one word, and that it is inoffensive. In addition, names of pets are discouraged, and any name that is of a commercial nature is not accepted.