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GiantSheeps
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Why isn't the Oort Cloud shaped like a disk like the asteroid belts and how the planets orbit? Also, why exactly do the planets orbit in that flat disk shape?
http://arstechnica.com/science/2014/03/new-dwarf-planet-found-sneaking-through-the-inner-oort-cloud/GiantSheeps said:Why isn't the Oort Cloud shaped like a disk like the asteroid belts and how the planets orbit? Also, why exactly do the planets orbit in that flat disk shape?
This is what I'm saying, yes. Oort cloud is essentially unaffected by density waves or physical interference from other bodies/dust/gas, leaving only the sun's gravity.Jimster41 said:... what is resonating or transmitting the density wave other than the relative positions of the objects (asteroids, rocks, planets, stars) in question?
I do believe I mentioned density waves isn't involved on the Oort cloudMordred said:though that's not too involved in the Oort cloud itself
Jimster41 said:So is the emergence of complex rotating structure rather than just one big disk or a crystal due to "various analogs of viscosity"?
Ken G said:Actually, it was my understanding that the Oort cloud came from strong perturbations due to close encounters within the Kuiper belt, or other initially flattened disklike distributions, especially involving interactions with Neptune or perhaps large asteroids. So if you imagine that you start out with a disk that is not perfectly flat, and let the objects in the disk have close gravitational encounters, they can pass above or below each other. But a close interaction like that can throw them out of the disk, onto highly inclined orbits. Many of these can extend out a long distance, where there can be interactions with other stars that don't conserve the angular momentum of the solar system. So I think it is those weak external interactions that cause the Oort cloud to be more spherical, more so than something about the initial formation of the solar system.
The basic idea, as I recall, is that when the solar system initially forms, the combination of energy loss (acting like viscosity) with having a lot of angular momentum is what forms a disk. This is because if you have a large amount of angular momentum, a disklike configuration has lower energy than a spherical distribution. So you get a disk as the solar system forms. But then you get strong interactions within that disk, because you have planets and large asteroids. That tends to disrupt the disk, and create a second component that is more spherical. Interactions with distant stars can also make it more spherical over time, even though it came from the disk originally. The details must be a bit complicated.Jimster41 said:Interesting. I was thinking that there must be a pretty good understanding of the angular momentum environment that a typical stellar disk evolves in? But I have no idea if that is so. I had pictured it as initially quiescent, and spherically symmetric. But maybe that is really wrong.
The whole nebula is not spherical, but the stars themselves are rather spherical. In between there are more and less spherical kinds of structures. For example, a proplyd is usually not too far from spherical, but inside there could be a disklike component, the part that has lost a lot of heat and contracted enormously. That's how you get disks.I've seen a lot of astronomy magazine picture of stellar nurseries. Doesn't seem like they start off quietly spherical, not at the point of ignition anyway.
Yes, planetary systems are generally quite disklike, especially around single stars. We often see these forming as what are known as T Tauri stars. The binary situation is much more complicated.Is it true that most solar systems are thought or observed to be disk-like?
That's a good question, I think the situation should be pretty similar indeed. There isn't the analog of a giant planet to throw out comets, but perhaps globular clusters can still get a pretty good orbital disruption without being broken apart.Is the "disturbed and ejected former members of the disk" model you seem to be describing a possible fit for galactic globular clusters also?
The disk comes from the presence of angular momentum, even a relatively small amount can make its presence felt. The exact source of that angular momentum I couldn't say, perhaps some kind of turbulence in a "windy" situation, but perhaps other things could do it without any prevailing winds.And is the idea that the solar system starts off more like a highly structured disk due to the highly ordered angular momentum ignition situation in "windy" stellar nurseries, where the direction/angle of the wind is defining the plane of rotation?
The Oort Cloud is not shaped like a disk because it is believed to be the remnant of the original protoplanetary disk that formed our solar system. This disk was likely spherical in shape due to the force of gravity pulling matter towards the center.
The shape of the Oort Cloud is influenced by the gravitational forces of the surrounding stars and the galactic tidal forces acting on it. These forces can distort the original spherical shape of the protoplanetary disk, resulting in a more elongated and scattered Oort Cloud.
The shape of the Oort Cloud affects the orbits of the objects within it. Due to its elongated shape, objects in the Oort Cloud may have more eccentric orbits, meaning they are more elongated and have a wider range of distances from the Sun.
It is possible for the shape of the Oort Cloud to change over time. As the Sun and our solar system continue to orbit around the center of the Milky Way galaxy, the gravitational forces acting on the Oort Cloud may cause it to become more spherical or elongated.
The shape of the Oort Cloud was determined through observations of comets that originate from this region. By studying the orbits and distribution of these comets, scientists were able to infer the shape and size of the Oort Cloud. However, since the Oort Cloud is so far away and difficult to observe, its exact shape is still not fully known and is subject to ongoing research and speculation.