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Why Do the Stars Twinkle in the Night Sky?

You lay back looking at the dark night sky covered with pinpricks of light. Stars shine brightly tonight! Some even seem to twinkle like light catching a sparkly bracelet. What makes them twinkle? 

Two adults and two kids sitting in the grass while looking up at the night sky.
(Photo via Shutterstock)

How many stars can you count on a clear night? Hundreds of billions of stars exist in the Milky Way, the galaxy that contains Earth and our solar system. It would take about 30 years of nonstop counting just to reach 1 billion! Imagine all the sand at all the beaches around the world. More stars exist in the Milky Way than grains of sand in the whole world. A lot more!  

Stars may look as tiny as grains of sand, but only because we see them from so far away down here on Earth. Do you think all stars are the same size? Nope. They grow to different sizes and even different ages, just like humans. But even the smallest star is bigger than Earth! The largest star is 2,000 times bigger than the sun! So think again about a grain of sand. Multiplied by 2,000 expands it to about the size of your front door! Now imagine that grain of sand as big as the sun. Can you even imagine the size that makes the biggest star? 

We have a close relationship with one star in particular — Earth’s sun! It looks much bigger and brighter than the other stars in the sky, even though many larger stars exist. Why do you think it looks so much bigger than all the rest? Because of its proximity (closeness) to us. See for yourself. Find two identical blocks. (Or balls or jars. Any two items that match in size.) Place one right in front of you and the other across the room or down the sidewalk. Do they look like different sizes now? Experiment by changing the distance or proximity of the block. It didn’t shrink; the proximity just changed.  


Words to know

Aerosol: A substance that when released under pressure comes a fine spray.

Atmosphere: The envelope of gases surrounding Earth or another planet.

Constellation: A group of starts forming a recognizable pattern.

Galaxy: A system of millions of billions of stars that is held together by gravitational attraction.

Proximity: Nearness is space, time or relationship.


Stars are huge balls of burning gas, so they shine with their own light. They burn night and day, but we can only see them when night falls. If they don't blink on and off like a lightbulb, why do they sometimes seem to twinkle? 

To view the stars from Earth, we look through layers and layers of atmosphere. A mix of 99% gases (mostly nitrogen and oxygen) and about 1% water vapor and aerosols (tiny particles of dust, spores, ash, smoke, salt and pollutants) make up the atmosphere. All those gases and particles moving through the atmosphere can bend starlight toward or away from our eyes, making the light twinkle. 

Want to see light bend up close? Fill a clear glass with water and add a straw. Look through the side. The straw looks broken because the light bends (or refracts) your view.  

That twinkle you see might not be a star at all. Planets can also seem to twinkle! Planets don’t shine with their own light, like stars. Instead, they reflect sunlight. Knowing our sun is a star, we could also say planets reflect starlight!  

A starry night sky with moon, Venus, and Jupiter in view.
A starry night sky with moon, Venus, and Jupiter in view. (Photo via Shutterstock)

Winter is a great time of year to stargaze because it gets dark out earlier. Try to find a place far from city lights that can brighten the sky, hiding the stars. Maybe your yard or a park or even a campground. Bring a blanket to sit or lay on and take in the view. Apps like SkyView Lite can help you identify the stars, constellations and planets by name. Maybe you’ll get lucky and wish upon a shooting star.  

Check out the Forest Preserve District of Will County’s event calendar for night hikes to explore the preserves after hours. Or reserve a campsite and fall asleep under the stars.


Follow Willy's Wilderness on Facebook for more kid-friendly nature stories and activities.


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