TNO

Trans-Neptunian object

Solar System
Trans-Neptunian object

any object in the Solar System that orbits the Sun at a greater average distance than Neptune

A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet or dwarf planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (AU).

Read on Wikipedia License Image-Source