A giant wave of gas crashes onto a dense ripple in this computer-simulated view of the solar nebula from which the Sun and planets formed. This is a side view of the disk, where whiter colors represent gas of higher density. The height of the wave is about half of the Earth-Sun distance at its highest point. The gas is thrown upward as it runs into a dense spiral ripple in the nebula, then curls over like a breaking wave and crashes back onto the disk. Arrows show the direction of gas flow. As the wave breaks, it forms a tube of low-density gas nearly 8 million miles (13 million kilometers) wide.