Why do planets and stars have a tendency to assume a disc-like configuration?

Question

Galaxies and solar systems tend to have a disc-like configuration. That is, the orbiting planets (in a solar sytem) and stars (in a galaxy) predominantly revolve around the center on a single plane. Why?

Answer 1

Scientific American had an article on this subject back in October 2004 called "A Universe of Disks".

http://www.sciamdigital.com/browse.cfm?sequencenameCHAR=item2&methodnameCHAR=resource_getitembrowse&interfacenameCHAR=browse.cfm&ISSUEID_CHAR=E9FFCBE6-2B35-221B-661ED2EFA6A79697&ARTICLEID_CHAR=EA105EB2-2B35-221B-60A972F6941696CE&sc=I100322



I can't remember details other than that the gas and debris interacts with each other to amplify a direction of rotation. I wouldn't be surprised if this ends up having an effect similar to an oblate spheroid such as earth except not enough gravity to pull it together so it continues to spread out like a pancake or one of those spin art pictures. Then since most of the matter is spinning in that direction it aggregates into the planets and planetoids.



But I could be wrong. Check out the article at your local library or buy a copy online.

Answer 2

Mass and Gravity. Need I say more?