The Kuiper Belt and Oort Cloud


The Kuiper Belt

On the far reaches of the solar system is an area of icy, small planetesimals called the Kuiper Belt. Named for astronomer Gerard Kuiper, who first theorized their existence, the Kuiper Belt is littered with thousands of icy-rock bodies from the size of a baseball to planetary bodies larger than Pluto. This disc-shaped region lies beyond Neptune’s orbit to a distance of about 56 AU from the sun. The Kuiper Belt presumably contains debris from the formation of the solar system 4.6 billion years ago.

Pluto and Eris are the best known residents within the Kuiper Belt. The Kuiper Belt and even more distant Oort Cloud are believed to be the home of comets that orbit our sun.

The Oort Cloud

Scientists hypothesize that the outermost region of our solar system is a giant sphere of objects made of icy ammonia, methane and water - the recipe for comets. Where the Kuiper belt is seen as on the same plane as the traditional planets, the Oort Cloud is a giant ball that encapsulates our solar system (See the picture on the right).

The Oort Cloud, first theorized by Jan Oort in 1950, is widely accepted by most astronomers although it has yet to be proven by any direct observations. Hopefully, the New Horizons space craft on its way to Pluto will also shed some light on the mysteries of deep space.

How big Could the Oort Cloud Be?

There has been considerable debate on this subject, yet no one really knows with any certainty. Some astronomers believe the cloud starts at about 2,000 AU from the sun and extends to almost a light-year away. Some believe it may stretch out double that amount! For our purposes, lets just say it is really big!

Comet Central!

The Oort Cloud is believed to be where most comets can be found. These ice balls can come into the inner solar system when passing objects knock them out of their orbits.

Short-term Comets

Long-term Comets

Most short-period comets come from the Kuiper Belt, while long-period comets come from the Oort Cloud. There are a few exceptions to this rule though. Halley’s Comet was a short-period comet that originated in the Oort Cloud.

Gerard Kuiper’s Contributions to Astronomy