Kuiper Belt vs Oort Cloud

[2763]

Can someone help me understand the difference between the Kuiper Belt and the Oort Cloud (in lay terms)? <br /><br />Are they both factual collections of objects, or are they still hypothesised? How are they physically related? Are they connected, or seperated by 'empty space'? Which is farther from the sun? Are their member bodies different in any known way (size, composition, etc)?

 

[Maddad]

In 1950 Jan Oort noticed that most comets had their aphelia, furthest distance from the sun, at about 50,000 times the distance from the Sun to the Earth, or astronomical units. Since the comets approached from any old direction, he proposed that they resided huge swarm in a shell 50,000 AU from the Sun. The gravity binding the comets to the Sun is so weak at this range than about any disturbance, such as a passing star, shakes a few of them loose to fall inward toward the Sun. This is how we currently explain the long period comets, those that show up once and then never again for hundreds of years.<br /><br />Short period comets behave differently though. They show up periodically, every 200 years or less, and they approach on the same plane or disk that the planets occupy. The do not approach from above or below the disk as the long period comet do. They have their aphelia at perhaps only 50 AU, about as far out as the furthest planet Pluto is. It appears that they are leftover material from the formation of the solar system.<br /><br />Twelve years ago we started finding the fist residents of this Kuiper Belt with the discovery of 1992 QB1. We've found a bunch more, which is amazing when you consider that you're looking for something the color of coal at maybe 4 or 5 billion miles away. More recently we have seen debris fields around other stars that are similar to our own Kuiper Belt.<br /><br />Our current best explanation for the more distant Oort Cloud is that all these objects were originally part of the Kuiper Belt and intermixing with the outer planets. As they came near the larger ones, especially Jupiter, the gravity tossed them into new orbits. When those orbits took them inside the solar system, then they eventually ran into a planet and disappeared from the scene. When they went outside the solar system then the took up residence where the Oort Cloud is now.

 

[centsworth_II]

My own vision:<br /><br />The Kuiper Belt objects are remains of the primordial matter that formed the planets. They were on the outer reaches of the disk-like cloud orbiting the sun from which the planets formed. Too sparce to form a planet and too far out to be disturbed by the other planets, they remain as a belt of objects orbiting the sun beyond the orbit of Pluto and in the same plane as that of the planets.<br /><br />The objects of the Oort cloud likewise are remnants of the primordial material from which the planets formed. However, they are from the region of the gas giants and so were not left to orbit the sun in peace. Those objects that were not sucked up in the formation of the gas giants were flung about by gravitational interactions with those large planets. Many were thrown out of the plane of the planets and far from the sun in all directions to form the Oort Cloud.<br /><br />The Oort cloud has not been seen. The objects forming it are too dark, small, far away , and sparce. Objects identified as being in the Kuiper belt have been seen, but not easily. So I would say that the Kuiper Belt is more of a physical reality while the Oort Cloud remains a good hypothesis. <div class="Discussion_UserSignature"> </div>

 

[Maddad]

That's a pretty good analysis.

 

[newtonian]

centsworth_II - The Oort cloud, like many extrasolar planets, while not seen is indicated by its effects. For example, note this quote:<br /><br />"We have never actually 'seen' the<br />Oort cloud. But no one has ever seen an<br />electron, either. We infer the existence<br />and properties of the Oort cloud and<br />the electron from the physical effects we<br />can observe. In the case of the former,<br />those effects are the steady trickle of<br />long-period comets into the planetary<br />system." - Scientific American, 9/98, page 84, article entitled "The Oort Cloud"<br /><br />Interestingly, the article goes on to show some close stellar encounters pass right through the Oort cloud, and molecular clouds also perturb the Oort cloud - and send some long period comets towards the inner solar system.<br /><br />Stars do not, however, perturb the Kuiper belt - they do not pass that close.<br /><br />Maddad- good post

 

[2763]

OK, so to boil this down to the most simple terms:<br /><br />1. We have not directly observed the Oort Cloud, but it's apparent that something of that nature is out there.<br /><br />2. The Oort Cloud is further out than the Kuiper Belt. <br /><br />3. We don't know if the Oort Cloud and Kuiper Belt are seperate systems or just one continuous collection of objects. <br /><br />4. The Oort Cloud is the likely source of comets, whereas Kuiper Belt objects stay in a more regular orbit outside of Neptune's. <br /><br />So did I get that right?

 

[roguesaint]

Looks good except for:<br /><br /><i>4. The Oort Cloud is the likely source of comets, whereas Kuiper Belt objects stay in a more regular orbit outside of Neptune's. </i><br /><br />The Oort cloud is the likely source of long-period comets. These are comets like Hale-Bopp that take thousands of years to make a single orbit. The short-period like Halley's (~76 year orbit) are likely Kuiper Belt objects. <div class="Discussion_UserSignature"> </div>