A Trans-Neptunian Object (TNO) is any celestial body located in the solar system beyond the orbit of Neptune. These objects primarily reside in the Kuiper Belt, a region filled with icy bodies and dwarf planets, including Pluto. TNOs can vary in size and composition, ranging from small icy bodies to larger objects like Eris. TNOs are significant for studying the early solar system, as they are considered remnants from its formation. They help astronomers understand the distribution of material in the outer solar system and the processes that shaped planetary formation.