Back to: Astronomy & the Cosmos
The Sun is a star, an ordinary one, which is precisely what makes it precious: it’s the only star close enough to study in detail. Like all stars, it is a giant ball of plasma powered by nuclear fusion: in its core, crushing pressure and temperatures around 15 million degrees Celsius fuse hydrogen into helium, converting a tiny fraction of mass into enormous energy. The Sun converts about four million tons of matter into light every second, and has been doing so for 4.6 billion years with about 5 billion to go.
A star’s life is a long tug-of-war between gravity pulling inward and fusion pushing outward. The single most important fact about any star is its mass, which determines everything: color, temperature, brightness, and lifespan. Counterintuitively, bigger means shorter-lived: massive blue stars burn their fuel furiously and die within a few million years, while small red dwarfs, the most common stars in the universe, will sip their fuel for trillions of years.
You can see this physics with your naked eye. Star colors are temperature readings: red-orange stars run ‘cool’ at around 3,000 degrees Celsius at the surface, our yellow-white Sun about 5,500, and blue-white stars 10,000 to 40,000 or more. When you compare reddish Betelgeuse to blue-white Rigel in Orion, you’re doing stellar astrophysics without instruments.