Why are the orbits of the planets in roughly the same plane?

In diagrams of the solar system the planets are shown orbiting the sun in roughly the same plane. Is this how it really works? Why can't they be skewed? (why can't they trace orbits on great circles that intersect in an angle like 90 degrees, for example) Are there other solar systems without this feature?|||Clouds of material will start spinning around a central 'clump' of material. Other 'clumps' will collect due to gravitational pull, and the larger clumps will pull the material orbiting in other planes down to it's plane of orbit, also because of gravitational pull. Eventually, *most* the material will be pulled into this single plane.





It's not a hard %26amp; fast rule that planets orbit in the same plane, or even in circular orbits - the Kepler Space Telescope is finding *dozens* of exceptions to just about every rule we thought were in place from large Jupiter-sized worlds orbiting in highly elliptical, comet-shaped orbits, to planets that seem to be orbiting *backward* from the rotation of their central star.





So far, nebular theory says that all *large* objects will eventually be pulled into a single plane of orbit, but we've seen some exceptions that may have been caused by encounters with other stars.|||Centrifugal effects are the reason.





The solar system started from a nebula (lump of gas). Over time gravitational attraction caused it to collapse in on itself.





The gas in the cloud, while moving fairly randomly, had a net bias in a particular direction. As the gas cloud collapsed this angular momentum is conserved and the rotation sped up (ala a figure skater pulling their arms in speeds up). In time everything gets spinning in the same direction and continuing to speed up.





As the collapse proceeds the centrifugal effect flattened out the gas into a disk. Same as a guy tossing pizza dough gets a flatter and flatter disk. Conservation of angular momentum puts the most stable orbits in the plane of the ecliptic (or near enough).|||Firstly, solar systems like our solar system are incredibly rare: most stars are just lone stars sitting in space. And second, that's just how gravity works. The planets at the edge of the solar system which are less affected by gravity, such as neptune and uranus(Giggle) have a slightly slanted orbit.|||They all formed from the same accretion disk, which forms in the equatorial, rotation plane, which would be fairly flat and in roughly the same plane as the Sun's equator.