What caused the disc-shape in the solar system?
Conservation of angular momentum if what causes clouds to flatten out into a disk. The interstellar dust and gas cloud that the Sun and Solar System formed from, along with other stars. started to rotate when the bow-shock wave of matter and energy from one or more relatively nearby supernovae encountered the interstellar dust and gas cloud. The other stars that formed at the same time that the Sun did dispersed long ago. If you want to look at a relatively young open star cluster that still has traces of nebulosity around it, look at the Pleiades with binoculars after sunset tonight. If you have REALLY good naked eye vision, you might even be able to see the tiny Little Dipper shape of the brightest of the Pleiades. There's another open cluster called the Hyades relatively close by that bright orange giant star Aldebaran is in front of. Aldebaran is the "eye" of the bull constellation of Taurus Clouds interstellar gas and dust clouds flatten out because of conservation of momentum mass and energy. This does NOT completely explain some planetary systems. When astronomers started discovering planetary systems with planets that revolve around their primary star in the opposite direction to the star's rotation, scientists originally said "That can't happen, because it violates the conservation of mass/matter, energy, and momentum". Some OTHER forces acted on planets with orbits like that AFTER the planets were formed. Scientists gave a name to the effect using the last names of two people that begin with "M" and "R." http://www.windows2universe.org/neptune/atmosphere/N_evolution_2.html AH HAH! This is why I don't clear Google search histories very often: http://en.wikipedia.org/wiki/Rossiter%E2%80%93McLaughlin_effect
Why is the solar system disc shaped?
Oh the answer is kinda cool.So in an early solar system you have this giant area of mostly hydrogen gas…and miscellaneous other elements and maybe molecules.Even though its gas it has a center of gravity. The solar system will spin ever so slowly around that center of gravity…But being the center of gravity, Lots of the matter in the solar system heads towards that location. As mass increases, spin increases…now you have this mass with a center of rotation. All of the mass in the solar system spins around that center of mass…following its spin.Planets are then formed on the enormous disc spinning around that proto star. And they then suck up the remaining material in the solar system….well except for the asteroid belt…kuiper belt…and oort cloud…but combined those enormous areas dont really have enough to build another planet.
Why is our solar system disc shaped? Is it the only shape in which planets can orbit our sun or are there other orbits (vertical to current axis) possible too?
A simple answer to that can be found here:But if you still wonder that why aren’t planets disk shaped too , that’s kind-of a different and question and I have already answered that here in detail :Yash Vardhan's answer to Why did gravity cause planets to form spheres but larger systems like solar system/galaxies to take a flat disc shape?
The Solar system is disc-shaped and it was formed from a disc-shaped cloud. Why can't the Earth be disc-shaped?
Strength of materials limits how tall a structure can be and a disc shaped celestial body would require structure to maintain that shape.Euler’s buckling theoryBuckling - WikipediaFrom the shapes of asteroids in the asteroid belt, it is obvious that when an accumulation of mass exceeds a certain size, gravity pulls the mass into a spherical shape.Things without structure like piles of sand or rocks fall down if piled steeper than what is called the angle of repose. Likewise anything not supported by a superstructure on a disc Earth would fall down to the center while the structure would too collapse from the implied instability of Euler’s theory. Gravity wins and we have a spherical world.
What is the approximate shape of the solar system?
The shape of the solar system is bullet-shaped.
What is the real shape of the solar system, sphere or flat? Does the Oort cloud contribute to the overall shape?
So to start off a rough definition of the phrase solar system.A solar system is a gravitationally bound system of objects orbitting a star.This essentially means that a solar system comprising of everything that is influenced by the sun's gravity, hopefully I got that right. This is a very large area and naturally it comprises of a 3D area. What most people consider the solar system is the system of planets from Mercury to Neptune with our little non planet friend Pluto hanging out outside. This also includes everything in between. There is also as you said an oort cloud that expands to include everything beyond pluto to the end of the gravitational influence of our Sun. There is a similar system for every solar system in the universe.
How is our Solar System really shaped?
There are really two questions here. (1) The exact shape of the planetary orbits, and (2) the shape of the solar system. I will briefly address both.If you looked at the planets from above (i.e. “normal” to) the solar system, you’d have difficulty’s making out anything outside the Sun. In the image below the orbits are colored, but the planets themselves are smaller than a pixel. Also you’ll notice that the orbits of all the planets are very circular (seen here as ellipses due to perspective). Sure, the orbits are not perfect circles, but except for Mercury and Pluto (not a planet!), the Orbital eccentricity of all the planets are less than 10%, making them nearly indistinguishable from a perfect circle to the naked eye. So the only orbits that clearly break the circular “bull’s eye” pattern are comets (one seen here) and Pluto (again, not a planet).However, in my mind the more interesting question is the second one: what is the shape of the whole solar system?, not just the inner/planetary part. To address this question we need to zoom out. Way out. And look at the largest structure in our solar system — the Oort cloud.Here the shape is much more complex and a topic of active study. However, in just a few words I’d describe the shape from this vantage point as a disk that flares outwards, until it becomes a thick spherical shell. Here are some illustrations:or, in a “logarithmic” view:
How are the solar system's planets aligned like a disk?
The solar system was formed using the “centrifugal matter distribution process”. When a mass of plasma has rotation, this process is what distributes the matter into the structures we see today. This process can be simultaneously applied to a galaxy, solar system, or a planet and it's moons or rings. Most structures are spiral in our universe but if the mass of plasma was created with little or no rotation, an “elliptical” object is created. These release matter from the center of the object.Our galaxy was a mass of spinning plasma. As it cooled, the centrifugal force spread the mass. The black hole separated first and left the remaining plasma disk to create all of the stars. Our solar system was one of those stars. It was a single mass of fusion powered plasma. It cooled and flattened just like our galaxy did. The sun separated first. Our planets were created in the remaining, orbiting, plasma disk. This disk is the answer to your question. This is how the matter was so perfectly placed for billions of years. Any matter in our solar system is extremely lucky to be here. Orbits are ludicrously fragile.
Why are galaxies, solar systems flat?
Good question, it had bugged me for a while.Let's go back to the beginning of things.A huge pandemonium of dust and gas, a nebula existed in a region, isolated from other infulence; but held together by mutual gravitation. Remember, conservation of angular (and, linear) momentum holds. Gravity pulls matter closer, things start getting hotter and denser.Things collide, as expected, this cancels out motion in opposing directions.(note: A and B are very much fluid i.e., they flow)The above process repeats again and again, thanks to the fluid nature, they finally become flatter.(Why flat? Continue reading)Things also spin faster, to conserve angular momentum in the event of reduction in moment of inertia. Things can stop colliding only if their paths don't intersect (and in case of intersection, they should have same velocity). In a fluid, this is achieved in a flat disc, thus, by definition, they are colliding until they become flat. (Reminder : we are assuming it's all gas and dust cluster and not the non-flowing solid.)Flat disc is the only shape that can have (A) matter that conserves angular momentum about the axis, (B) Doesn't collide, even when gravity pulls it. I challenge you to come up with any other shape, which does the same things for a gas cloud, in our 3D physical universe.Thus, the combined effect of collision and the fact that things have to conserve momentum about a given axis, leads to flatter galaxies which spin about an axis.In case, my explanation sucks, as I am afraid it does, check this out.