Why Do Stars Twinkle? — For Kids

Why Do Stars Twinkle? — Elementary

The short answer

Stars look like they twinkle.

But most stars do not really change.

Most stars shine with a steady light.

The twinkle happens in the air above us.

Moving air bends the starlight a little bit.

How many stars can we see?

Pick a clear, dark night.

Our eyes can see about 6,000 stars in the sky.

They seem to twinkle all the time.

They seem to change how bright they are.

What bends the light?

The air around Earth is called the atmosphere.

The air in the atmosphere moves.

Moving air is sometimes called turbulence.

Starlight travels from a far away star.

It travels through the atmosphere.

Then it comes down to us on the ground.

The moving air bends the light a little bit on the way.

Some of the light reaches us.

Some of the light bends a little bit away.

To our eyes, that makes the star seem to twinkle.

Stars low in the sky twinkle more

Look at a star near the horizon.

The horizon is low down, where the sky meets the ground.

That star will seem to twinkle more.

There is a lot more atmosphere between you and that star.

A star higher in the sky has less atmosphere in the way.

So the low star twinkles more than the high star.

Try it yourself

Go out some night soon and have a look!

Check a low star.

Then check a high star.

See which one twinkles more.

And remember: stars do not blink their eyes.

They do not have any!

Why Do Stars Twinkle? — Middle

The short answer

Stars seem to twinkle — to change their brightness all the time — but most stars are actually shining with a steady light.

The twinkle is added on the way down: movement of air in Earth’s atmosphere bends the starlight slightly, so some of it reaches us and some of it bends away.

Steady stars, moving air

On a clear, dark night, our eyes can see about 6,000 or so stars in the sky, and they seem to twinkle the whole time you watch them.

In fact, most of the stars are shining with a steady light. The change you see does not start at the star.

Starlight travels from the distant star through Earth’s atmosphere, down to us on the ground.

The air in the atmosphere moves. That movement of air is sometimes called turbulence.

The turbulence causes the starlight to get slightly bent as it travels through the atmosphere.

Why bent light looks like a twinkle

Because the light gets bent, some of the light reaches us directly and some gets bent slightly away.

How much light reaches your eyes keeps changing as the air keeps moving.

To our eyes, that changing amount of light makes the star seem to twinkle — to change its brightness again and again.

So the star’s own light stays steady, and the bending in the air above us does the twinkling.

Why stars near the horizon twinkle more

You will notice that stars closer to the horizon appear to twinkle more than other stars.

That is because there is a lot more atmosphere between you and a star near the horizon than between you and a star higher in the sky.

Light from a low star has more atmosphere to travel through, so it has more chances to get bent on the way down.

Light from a star higher in the sky passes through less atmosphere, so it gets bent less.

Try it yourself: go out some night soon and have a look — compare a star near the horizon with one higher up.

One last note from the source: stars do not blink their eyes (they don’t have any!), tip their hats, or take a bow.