The disk spins, rotating around its center like a DVD (though stuff toward the center goes around faster than stuff near the outer edge). The middle of the disk is where the star forms. Farther out, local eddies and vortices can form planets. But the important thing to note is that in this scenario, everything spins in the same way. If the disk appears to be spinning clockwise, say, then the star will spin that same way, the planets will orbit that same way, and the planets will spin that same way. We’re pretty sure this is how things work because that’s pretty much what’s happening in our own solar system.
This theory has been tested by observation and by increasingly complex modeling. Sometimes there are problems with it, but in general new ideas have been added that fix those problems, and over time we’ve been pretty happy overall with the idea that stars and planets form this way.
However, a bunch of newly discovered planets have messed this nice idea up. They orbit their stars the wrong way!
Tuesday, April 13, 2010
Well, not really: