Science
What is a Star?
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.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains a star.
Key things to understand
- 1A star is a massive sphere of plasma, mostly hydrogen and helium, held together by gravity.
- 2It shines because nuclear fusion in its core turns hydrogen into helium, releasing light and heat.
- 3Stars form from collapsing clouds of gas and dust, live for millions to billions of years, then die — sometimes in a supernova.
- 4The Sun is our nearest star; others look like tiny points only because they're so far away.
- 5Stars vary hugely in size, colour, and temperature — blue stars are hottest, red ones coolest.
Frequently asked questions
- 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.