A cold cloud falls in on itself. Gas piles up in the middle, but there is no Sun yet. The light has to wait.
If you have watched a skater pull their arms in, you have seen the trick this cloud is about to try. As it shrinks, its slow turn speeds up. The gas whirls faster without a fresh push.
Gas bumps into gas. Upward and downward motions cancel, while the shared spin keeps going. The cloud flattens into a disk, with dust circling the growing lump at its heart. Planets will grow from those scraps.
Now the squeeze gets fierce. Think of a bike pump warming in your hand as you press it. Deep inside the cloud, heat lets hydrogen atoms join together. That is fusion: small atoms joining and giving off energy. The energy pushes back against gravity. A star can shine.
We can watch young stars with dusty disks today. Dark gaps cut through some disks, where growing planets may be clearing a path. Scientists still argue about what makes each gap. But the disks are real. A telescope can catch the dust around a young sun.
