Where do comets come from?
There are two types of comets short-period and long-period comets. Short-period comets come from a KUIPER BELT ( a material belt ), which is in fact beyond Pluto. On the other hand, long-period comets come from the ORT CLOUD (a circle of rocks at the edges of the solar system). What does a comet consist of? There are five main parts to the comet. The first being the NUCLEUS, is made up of solid ice, small dust and gas. The COMA, another main feature of the comet, is a cloud made up of water and Carbon Monoxide which surrounds the nucleus. There is also the HYDROGEN CLOUD, which is an enormous cloud surrounding the comet which ranges in millions of kilometers in diameter. The DUST TAIL, is a trail leading from the comet that can be as long as ten million kilometers long which consists of dust the particles/debris from the comet. Lastly, the ION TAIL, which is a tail leading from the comet where the size is approximately a hundred million kilometers long. click on image to enlarge-Diagra
Comets are balls of ice and other material that can be ‘left overs’ from the formation of a solar system (ours or others). A solar system forms when a swirling cloud of gas and dust condenses enough to start an ongoing nuclear reaction in the middle of it – that’s the star. The rest of the gases and dust ‘accrete’ (gather together via gravitational forces) to eventually form planets. Not all of this material ends up in the planets and their moons. It is this material that can wind up in a comet.
Comets come from two major areas of our solar system: the Kuiper (pronounced KY-per) Belt and the Oort (pronounced OR-t) Cloud. Each of these regions contains billions of comets, but they have so much room in these vast rooms of space that they get no closer to each other than we on Earth do to the sun.
Comets are believed to have two sources. Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt. Danish astronomer Jan Oort proposed that comets reside in a huge cloud at the outer reaches of the solar system, far beyond the orbit of Pluto. This has come to be known as the Oort Cloud. Statistics imply that it may contain as many as a trillion comets and may account for a significant fraction of the mass of the solar system. However, since the individual comets are so small and so far away, we have no direct evidence about the actual existence of the Oort Cloud.
Mathematical theory suggests that most comets may come to the solar system from very far away, as far away as 100,000 AU. An AU is the distance from the earth to the sun and is roughly equivalent to 100,000 miles. Mars is 1.5 AU from the sun, Jupiter is 5 AU from the sun, and Pluto is 39 AU from the sun. So comets come from very far away indeed. Comets are observed to come to the solar system from all directions, therefore the place where the comets come from is thought to be a giant sphere surrounding the solar system. This sphere is called the Oort cloud. Thus comets are said to come from the Oort cloud. But some comets may come to the solar system from closer in. The place where these comets come from is called the Kuiper Belt, which is located past the orbit of Pluto. It is natural to ask How did comets get so far away?
