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What is a star?
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Quick answer
A star is a giant ball of hot, glowing gas (plasma) held together by its own gravity, that shines by producing energy through nuclear fusion in its core. Our Sun is a star, and the night sky is full of distant ones, each a sun of its own.
Key things to understand
- A star is a massive sphere of plasma, mostly hydrogen and helium, held together by gravity.
- It shines because nuclear fusion in its core turns hydrogen into helium, releasing light and heat.
- Stars form from collapsing clouds of gas and dust, live for millions to billions of years, then die — sometimes in a supernova.
- The Sun is our nearest star; others look like tiny points only because they're so far away.
- Stars vary hugely in size, colour, and temperature — blue stars are hottest, red ones coolest.
People also ask
Why do stars shine?
Nuclear fusion in their cores fuses hydrogen into helium, releasing vast energy as light and heat — the same process that powers the Sun.
Is the Sun a star?
Yes. The Sun is a fairly ordinary star — it just looks far bigger and brighter than the others because it's so close to us.
What happens when a star dies?
It depends on its mass: small stars fade into white dwarfs, while massive stars explode as supernovae, sometimes leaving behind a neutron star or black hole.