A star is a giant ball of very hot gas, mostly hydrogen, that gives off light because nuclear reactions deep inside it release huge amounts of energy.

Yes. The Sun is a star, just much closer to Earth than any of the others. Every star you see at night is similar to the Sun, only farther away.

How many stars are in the universe?

Astronomers estimate there are more stars in the observable universe than grains of sand on every beach on Earth combined: roughly 10 to the power of 22 to 24.

Stars · Glossary · Aura Looks Up

Q: Why do stars twinkle?

Stars themselves don't twinkle. Their light is bent slightly as it passes through Earth's atmosphere, and that small bending makes the light look like it's flickering from the ground.

A star is a giant ball of super hot gas that glows. From here on Earth, stars look like tiny twinkling dots in the night sky. But they're actually huge. Bigger than mountains. Bigger than Earth. Some are bigger than a million Earths put together!

Why do they look so small?

Because they're really, really far away. Even the closest star (besides our Sun) is so far that a rocket would take thousands of years to reach it.

Wait, is the Sun a star?

Yes! The Sun is just a star that's close to us. That's why it looks bright and big. All the other stars in the sky are like the Sun, just much, much farther away.

Why do stars twinkle?

Stars don't actually twinkle. Their light gets a little wobbly as it passes through Earth's air. So when you see a star "twinkle," you're really seeing the air bend its light back and forth, kind of like how a coin looks wobbly under water.

How many stars are there?

Way more than you can imagine. There are more stars in the sky than grains of sand on every beach on Earth, all added up. The universe is packed with them.