Life on the Main Sequence

Main-sequence stars are the workhorses of the universe:

• Hydrostatic equilibrium keeps the star stable for millions to trillions of years
• The HR diagram maps stars by temperature and luminosity, revealing the main sequence
• A star's mass sets its color, temperature, luminosity, and lifespan
• Red dwarfs make up about 75% of all stars and can burn for trillions of years
• Fusion in the core powers everything, converting hydrogen into helium

The Sun is a middle-aged, average-mass star. It is not special by stellar standards, but that very ordinariness is what makes it stable enough to support life for billions of years.