Koid

Koid is a term used in the field of astrophysics to describe a small, icy body that orbits the Sun. These objects are typically found in the outer regions of the Solar System, beyond the orbit of Neptune. Koids are believed to be remnants from the early Solar System, and their study provides valuable insights into the formation and evolution of planetary systems.

The term "koid" is a portmanteau of "Kuiper" and "oid," named after the Dutch-American astronomer Gerard Kuiper, who proposed the existence of a belt of icy bodies beyond Neptune in the 1950s. The Kuiper Belt, also known as the Edgeworth-Kuiper Belt, is a region of the Solar System that extends from about 30 to 55 Astronomical Units (AU) from the Sun. It is home to many koids, including the dwarf planet Pluto.

Koids vary in size, with some being as small as a few kilometers in diameter, while others can be hundreds of kilometers across. They are primarily composed of ice and rock, and their surfaces are often covered in a layer of frozen gases such as methane and nitrogen. Some koids, like Pluto, are known to have their own moons.

The study of koids is an active area of research in astrophysics. Scientists use telescopes and spacecraft to observe and analyze these objects, aiming to understand their composition, origin, and the role they play in the dynamics of the outer Solar System. Notable missions, such as NASA's New Horizons, have provided close-up images and data from koids, including Pluto and its moon Charon.