Nearplanetary

Nearplanetary refers to a category of celestial bodies that are similar in size and composition to planets but do not meet the criteria to be classified as such. These objects are typically found in the outer regions of the solar system and are often characterized by their icy compositions and irregular shapes. Nearplanetary objects are of particular interest to astronomers and planetary scientists due to their potential to provide insights into the early solar system and the processes that led to the formation of planets.

One of the most well-known nearplanetary objects is Pluto, which was reclassified as a "dwarf planet" by the International Astronomical Union in 2006. Other notable examples include Eris, Makemake, and Haumea, all of which are located in the Kuiper Belt, a region beyond Neptune's orbit that is populated with numerous icy bodies. These objects are often studied using ground-based telescopes and space missions, such as NASA's New Horizons, which conducted a flyby of Pluto in 2015.

The term "nearplanetary" is not officially recognized by the International Astronomical Union, but it is used informally by some astronomers to describe objects that are similar in size and composition to planets but do not meet the criteria for planetary status. These objects are often referred to as "planetary-mass objects" or "planetary embryos" and are thought to have played a significant role in the formation and evolution of the solar system.