Core Intelligence Points
- Stars shine because of nuclear fusion.
- Gravity compresses gas until fusion begins.
- Mass controls how a star lives and dies.
Full Technical Analysis
A star is a self-sustaining nuclear engine held together by gravity. It begins as gas—mostly hydrogen—that collapses inward under its own weight. As the gas compresses, the temperature and pressure in the core rise dramatically.
When conditions become extreme enough, hydrogen atoms fuse into helium. This fusion releases enormous energy in the form of light and heat. That outward energy balances gravity’s inward pull, creating a stable object that can shine for millions or even trillions of years.
The single most important property of a star is its mass. Mass determines how hot the core becomes, how fast fuel is consumed, how bright the star shines, and how it will eventually die. Everything else in stellar evolution flows from this one factor.