2006-08-29 13:28:00 · 9 answers · asked by Chase 4 in Science & Mathematics ➔ Astronomy & Space
The Oort cloud is a postulated spherical cloud of comets situated about 50,000 to 100,000 AU from the Sun. This is approximately 2000 times the distance from the Sun to Pluto or roughly one light year, almost a quarter of the distance from the Sun to Proxima Centauri, the star nearest the Sun.
Although no direct observations have been made of oort cloud, it is believed to be the source of most or all comets entering the inner solar system (some short-period comets may come from the Kuiper belt), based on observations of the orbits of comets.
2006-08-29 13:31:32 · answer #1 · answered by knowbuddycares 3 · 3⤊ 0⤋
Oort Cloud
Another outer region of the solar system is the Oort Cloud, a theoretical cloud of comets that surrounds the solar system out to a distance of two light-years (11.36 trillion miles). The Oort Cloud was first proposed by Jan Oort in 1950. This "land of comets" contains comet-forming nuclei left over from the formation of the solar system. It is currently thought that this is the location where all comets originate, and it is the current origin of long-period comets. The way they enter the inner solar system is by gravitational pushes usually caused by a passing star.
The Oort Cloud is a generally accepted theory, though no member of the Oort cloud has been conclusively found. The object "Sedna" that was announced on March 15, 2004, is a possible member of the inner Oort Cloud. Its orbit takes it to within 90 A.U., but as far out as about 900 A.U. from the Sun. It is believed to be about 75% Pluto's size, with a radius of 950±150 km. It is the coldest object in the solar system with a surface temperature of -240 °C (-400 °F), and it is also a very red object - the reddest in the solar system other than Mars. It was originally believed that Sedna had a moon, but that was based upon an erroneous measurement of its "day," which was more accurately determined in 2005 to be about 10 hours instead of 20 Earth days.
Sedna is the farthest known solar system object, and it has a period of 10,500 years. It is still, however, not representative of the Oort Cloud. As shown in the lower left panel of the diagram on the right, Sedna is still well within what was believed to be the inner boundary of the Oort Cloud. For this reason, the Oort Cloud is still hypothetical, with no direct evidence that it exists. But the search is still on.
2006-08-29 15:13:26 · answer #2 · answered by hamdi_batriyshah 3 · 1⤊ 0⤋
There's very little mass out there, and it is so finely-divided that it would be hard to see even if it was not also so far away! Have you ever been out driving and driven into a foggy valley? From a distance, you can see the fog, because it is thick enough to block the light. But, as you get close to it, you start getting into it before you realize you are in the midst of it! There's some mass there (the water) but because it is finely-divided (in the form of water vapor) it is almost unnoticeable.
That's what the Oort cloud is like. The planetoids out there are relatively small pieces, few larger than about 1000 miles. If you gathered up all the mass in the Oort cloud, it probably would not be much larger than Earth. But it is spread throughout a volume of space much larger than the rest of the solar system!
Besides, that, it is very much farther from the Sun than Pluto is, and it is hard to see thing when they don't reflect much light.
2006-08-29 13:51:29 · answer #3 · answered by cdf-rom 7 · 0⤊ 0⤋
We're fairly sure the Oort cloud exists. Certainly there must be some explanation for the continual presence of comets in the inner solar system - the solar wind melts them too quickly for them to have survived from the formation of the solar system.
Why can't we see it? Well, we may have seen a little of it already, in fact - 90377 Sedna is suspected to be an inner Oort cloud object, and there are (dubious) reports of astronomers having found other such objects in Hubble Space Telescope photos. However, since the objects in the cloud are so small and far from the sun, finding them is no mean task.
2006-08-29 13:40:20 · answer #4 · answered by peri_renna 3 · 0⤊ 0⤋
Go to nasa.gov and search "Sedna".
Discovered in 2003 it is the largest object known beyond Pluto. It is also the second reddest object (after Mars). With a diameter around 1,000 miles and orbiting the sun 8-84 billion miles away, it took a very sophisticated telescope to discover it: the 48-inch Samuel Oschin Telescope at Caltech's Palomar Observatory.
Interestingly, it may be part of the Inner Oort Cloud, formed by a star that came close to our Sun and may have precipitated lethal comet showers on Earth billions of years ago.
2006-08-29 13:50:46 · answer #5 · answered by jorge f 3 · 0⤊ 1⤋
Yes it exists. Soppose you're at a bonfire party in a large paddock on a dark night. Whether you can see one of your fellow guests depends on two things; how far away she is from you and how far she is from the bonfire. The Oort cloud objects are a long way from us and from the Sun, and they're small.
2006-08-29 13:35:49 · answer #6 · answered by zee_prime 6 · 1⤊ 0⤋
Yes. We do see it, in the comets that occasionally come close to earth. When you trace back the trajectories, it's the Oort cloud.
2006-08-29 18:17:41 · answer #7 · answered by Tekguy 3 · 0⤊ 0⤋
Go to wikipedia.org and search oort cloud - then go to solarviews.com and again search oort cloud - you'll have a ton of explanations, theories, pictures, etc. - Why we can't see it? - probably because it is estimated to be from 1 to 3 light years away.
2006-08-29 13:36:42 · answer #8 · answered by poormigalito 3 · 1⤊ 2⤋
Well yes...they is where comets come from.
We can't see it because it's to far and the objects are to small without enough reflectivity.
2006-08-29 13:32:24 · answer #9 · answered by Scott A 2 · 1⤊ 0⤋