Evolution of the streaming instability in a 3D local shearing box. The movie shows the mass column density of particles in the radial (x)-azimuthal (y) plane. Initially, the streaming instability sets in, leading to particle clumping. At time 1:55, self-gravity is turned on (the color scale re-adjusts at this point), and the particles collapse to planetesimal mass scales.
Because it leads to the clumping of particles, this instability is important in the early stages of planet formation.
JILA, University of Colorado 440 UCB Boulder, CO 80309