Kuiper Belt and Kuiper Belt Objects

Kuiper Belt or the Kuiper-Edgeworth Belt is a doughnut-shaped region that extends between about three to eight billion miles (5 to 12 billion kilometers) out from the Sun (its inner edge is about at the orbit of Neptune, while its outer edge is about twice that diameter).

Kuiper Belt Objects

Kuiper Belt Objects (KBOs) are objects that originate from or orbit in the Kuiper Belt.

Only one KBO was known for more than 60 years: Pluto.

Largest KBOs in solar system: (Diameter: km)

Eris → 2300-2400

Pluto → 2,306

Sedna → 1,500

Quaoar → 1,260

Charon → 1,210

Orcus → 940

Varuna → 890

Ixion → 820

Chaos → 560

Huya → 500

Many KBOs have been discovered since 1990s, however, and the current estimate is that there are millions of KBOs.

KBOs are basically comets without tails, i.e. icy dirtballs that have collected together over billions of years. If they get large enough—such as Pluto did—they evolve as other massive planet like bodies do, forming dense cores that have a different physical composition than the mantle or crust above it. Most short-period comets— those with relatively short orbital times of a few years to a few centuries—are thought to originate from the Kuiper Belt.

Plutinos

Plutinos are Kuiper Belt Objects that are smaller than Pluto, have many physical characteristics similar to Pluto, and orbit around the Sun in much the same way that Pluto does.

The discovery of Plutinos led to the recognition that the Kuiper Belt is heavily populated, and that Pluto itself is a Kuiper Belt Object.