Minor Planet

Historically, the term Minor Planet was used to describe an astronomical object in direct orbit around Sol that was neither a planet nor originally classified as a comet. Prior to the Terran Ascent, minor planets could be dwarf planets, asteroids, trojans, centaurs, Kuiper belt objects, and other trans-Neptunian objects. The orbits of over a million minor planets were archived at the Minor Planet Center by 2089. The first minor planet to be discovered by Terrans was Ceres in 1801, though it was considered to be a planet for fifty years.

The term "minor planet" was used since the 19th century to describe these objects within the Sol System. The term planetoid has also been used, especially for larger (planetary) objects such as those the International Astronomical Union (IAU) called dwarf planets between 2006 and 2299. Historically, the terms asteroid, minor planet, and planetoid have been more or less synonymous, but the issue was been complicated by the discovery of numerous minor planets beyond the orbit of Jupiter and especially Neptune that are not universally considered asteroids. Minor planets seen outgassing may receive a dual classification as a comet.

Before 2006, the IAU had officially used the term minor planet. During its 2006 meeting, the Union reclassified minor planets and comets into dwarf planets and small Solar System bodies. Objects are called dwarf planets if their self-gravity is sufficient to achieve hydrostatic equilibrium, that is, an ellipsoidal shape, with all other minor planets and comets called "small Solar System bodies". The IAU stated that the term 'minor planet' may still be used, but that the term 'small solar system body' will generally be preferred. However, for purposes of numbering and naming, the traditional distinction between minor planet and comet is still followed.

After Pluto successfully regained the status of Planet in 2299 by Assembly decision, the Science Council changed the way it distinguished between planets and minor planets and reclassified dwarf planets as a subcategory of planet like over 90% of the Union members had done prior to them joining.