Trans-Neptunian Objects (TNOs) are celestial bodies that orbit the Sun at distances greater than Neptune's average orbital distance of 30 astronomical units (AU). These fascinating remnants from our solar system's formation inhabit the outer reaches of space, where sunlight is incredibly faint and temperatures plummet below -200°C.</p><p>TNOs are classified into three main groups based on their orbital characteristics. Kuiper Belt Objects, like the famous dwarf planet Pluto (discovered in 1930), orbit in a relatively stable disk between 30-50 AU from the Sun. Scattered Disk Objects follow highly elliptical paths that can stretch far beyond 100 AU, exemplified by Eris, whose discovery in 2005 sparked the reclassification of Pluto as a dwarf planet. Detached Objects maintain mysterious orbits completely separated from Neptune's gravitational influence, such as Sedna, which travels as far as 937 AU from the Sun.</p><p>Since the first Kuiper Belt Object discovery in 1992, over 3,000 TNOs have been cataloged, with estimates suggesting hundreds of thousands more await detection. These primitive, icy worlds preserve pristine materials from the solar system's birth 4.6 billion years ago, making them invaluable time capsules for understanding planetary formation. Their study continues to reshape our comprehension of the solar system's architecture and evolution.