A field guide to making a sun
How a cold cloud learns to burn — in four movements.
I — The Cloud
Ninety light-years of hydrogen and dust, ten degrees above absolute zero. Nothing happens here for a very long time — until something nudges it.
II — Collapse
The cloud falls inward and, falling, begins to spin. Spin flattens it into a disc that feeds its own centre — a protostar, glowing only from the heat of being crushed.
III — Ignition
At the core, hydrogen nuclei finally touch. Fusion pushes back against the fall; the star stops collapsing and starts to shine, and its light sweeps the disc clean.
IV — Afterglow
Barely one percent of the cloud is left over. It is enough. Grit becomes rock, rock becomes worlds, and one of them cools enough to hold an ocean.
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