Science's Not Boring

What is a star made of?

SCL Season 1 Episode 345

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0:00 | 14:23
Look up at the night sky! Have you ever wondered what those tiny, twinkling lights actually are? Join Mira and Finn on a wild cosmic journey to uncover the secret lives of stars! You'll discover that our Sun is actually a giant, roaring fireball reaching a mind-blowing 27 million degrees Fahrenheit at its core. But what is it made of? Hint: It's not fire! Learn how hydrogen and helium crash together in an explosive process called nuclear fusion to create blinding light. We'll solve the mystery of why stars seem to twinkle and flicker—it’s actually Earth's wavy air playing tricks on your eyes! Then, prepare to have your mind blown by the terrifying Red Hypergiant star, Stephenson 2-18, which is so massively huge it could swallow up the entire planet Saturn! Finally, find out what happens when giant stars run out of fuel and blast across the galaxy in a spectacular supernova. You'll even learn a crazy, true secret: you are made of star-stuff, and the iron in your very own blood was made inside an exploding star billions of years ago! Get ready to launch into this amazing space adventure!
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Welcome to Science Is Not Boring by Kidopoly.com. I'm Mira. And I'm Finn. Let's get ready for some wild science.

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Finn, close your eyes and imagine a giant, roaring fireball floating in the pitch black, freezing cold of space.

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Okay, I'm picturing it. Is it huge? Like bigger than a whole planet?

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Beyond huge! And at the very centre of this fireball, the core temperature reaches an absolutely mind-blowing 27 million degrees Fahrenheit.

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27 million degrees? That would melt literally anything we have on Earth in less than a second. Where is this super hot monster hiding?

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It's not hiding at all. You see it every single day. It's our sun. And it is just one of billions and billions of stars out there in the universe.

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Whoa! When I look up on a clear night, the sky just fills with these tiny twinkling points of light. They don't look like giant fireballs at all.

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That's exactly what we are investigating today. We are going to find out what stars are actually made of, why they produce so much blinding light, and why they seem to flicker and dance as you watch them.

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And I want to know about the scary ones. Are their stars way bigger and hotter than our sun? What happens when they finally die?

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We are covering all of that. We will discover the secret lives of the stars, from the glowing clouds where they are born, to their massive, dramatic endings.

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Get ready to launch. So, if our sun is a star and the stars in the night sky are just like it, what exactly are they made of? Are they made of fire?

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Actually, no. They look like fire, but stars are giant glowing balls of scorching hot gas. Specifically, two main gases make up almost the entire thing. Let me guess.

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Oxygen? We need oxygen for campfires on Earth.

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Nope. Space doesn't have oxygen floating around like we do. A normal star is made of about 73% hydrogen and 25% helium.

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Helium? Like the stuff we put in party balloons to make them float to the ceiling.

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Exactly the same stuff. But inside a star, that gas is under so much pressure from gravity that it does something incredible. It triggers a process called nuclear fusion.

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Nuclear fusion? That sounds intense. What does it actually do to the gas?

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Gravity crushes the tiny hydrogen atoms together so hard and so fast that they actually smash into each other and fuse to become heavier helium atoms. And that smash releases a ton of energy. Bingo! Every single second, our sun turns 600 million tons of hydrogen into helium. It's a continuous, gigantic reaction. 600 million tonnes?

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A second? That's like hundreds of millions of heavy elephants crashing together all at once.

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That's a hilarious way to picture it. And all that explosive energy pushes outward, which perfectly balances the gravity trying to crush the star completely. It's an ultimate cosmic tug of war.

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So a star is literally just gravity pulling inward and nuclear explosions pushing outward, holding perfectly still. That is awesome.

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You got it. And that explosive outward energy creates the intense light and heat, which travels 93 million miles through the freezing vacuum of space to reach our planet and keep us warm.

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Okay, so if stars are giant nuclear reactors blasting out pure light, why do they twinkle? When I look up, they look like they are blinking on and off.

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That is one of my favourite science illusions. The stars aren't actually blinking at all. They shine with a steady, fierce light. The twinkling is actually Earth's fault.

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Earth's fault? What is our planet doing to the light? It's just sitting here.

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Scientists call the effect stellar scintillation. Try saying that five times fast.

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Stellar scintillate, scintill. Nope, I can't even say it once. What does it mean?

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It means the light from a star travels in a perfectly straight line for trillions of miles. Take the closest star to us, Proxima Centauri. It's about 25 trillion miles away.

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25 trillion miles in a completely straight line? But then what happens when it hits Earth?

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Right before it reaches your eyeball, it has to travel through Earth's atmosphere. And our atmosphere is constantly swirling with moving air, heavy wind, and changing temperatures.

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Oh, like when you look over a super hot blacktop road in the summer and the air looks all wavy and blurry.

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Yes, you nailed it! The hot and cold air layers in the atmosphere act like giant, invisible, wobbly lenses. They bend the starlight back and forth, zigzagging it in a fraction of a second.

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So the beam of light shifts around, and to our eyes, down below, it looks like it's flickering or changing brightness. Exactly.

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If you were an astronaut standing on the moon, which has no atmosphere, the stars wouldn't twinkle at all. They would just look like solid, piercing dots of light in the black sky.

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No way! I want to see a non-twinkling star. But wait, do planets twinkle too?

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Great question! Planets like Venus or Jupiter usually don't twinkle. Because they are so much closer to us, they appear as tiny disks of light, not single points. Their thicker beams of light push through the wavy air much easier.

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So we know they are made of gas, and they twinkle because of our wobbly air. But what about their secret lives? Are their stars way bigger than the sun?

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Finn, prepare to have your mind absolutely blown. Our sun is what astronomers call a yellow dwarf star. It's actually pretty average.

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A dwarf? You could fit a million Earths inside it.

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How is that a dwarf? Because space is ridiculous! Let me introduce you to one of the absolute giants of the known universe. A red hypergiant star named Stevenson 218.

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Red hypergiant sounds like a terrifying boss in a video game. Just how big is it?

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Imagine placing Stevenson 218 right where our sun is, in the exact centre of our solar system. It is so astronomically huge that it would swallow up Mercury, Venus, Earth, Mars, Jupiter, and Saturn.

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It would eat Saturn's rings? That's wait, how wide is that in miles?

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It is roughly 2,150 times wider than our Sun. If you flew a standard passenger airplane around it at normal speed, it would take you 1,200 years just to make one trip around its equator.

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1,200 years on an aeroplane? I would need so many tiny bags of peanuts.

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You definitely would. But here's the wild part. The biggest stars don't actually live the longest. Because they are so massive, they burn through their hydrogen fuel incredibly fast.

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How fast? Like a few weeks?

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Fast for a star. Our little yellow sun will live for a totally peaceful 10 billion years. But a supergiant might only live for a few million years before it completely runs out of fuel.

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What happens when it runs out? Does it just go dark?

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Far from it. The core collapses in on itself in a fraction of a second and then blasts its outer layers across the galaxy at millions of miles per hour. It's called a supernova, and it shines brighter than a whole galaxy of normal stars.

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That is equal parts terrifying and completely awesome. But what happens to all that exploded star stuff? Does it just float around in the dark forever?

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It actually creates us. The famous astronomer Carl Sagan once said, we are made of star stuff, and he meant it literally.

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Wait, I'm made of star stuff? I definitely don't feel like a glowing ball of nuclear gas.

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Well, in the extreme, unbelievable heat of a dying star's supernova, the explosion creates heavy elements. The iron in your blood, the calcium in your bones, and the carbon in your muscles were all originally forged inside the core of a star.

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Are you serious? The iron in my blood actually came from a giant supernova explosion billions of years ago.

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100% real science, Finn. Without dying stars sharing their materials, there would be no rocky planets like Earth, no oceans, and no life at all.

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That is the coolest thing I have ever heard. I'm literally a supernova survivor. I have space metal in my veins.

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We all do. It's the ultimate connection to the universe. Now, how about a quick, mind-blowing fun fact about the stars we see?

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Hit me, I'm ready for more space craziness.

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Have you ever wished upon a fast-moving shooting star?

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Yeah, all the time. I saw a super bright one last summer zipping right across the sky.

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Well, shooting stars aren't stars at all. They are actually tiny pieces of space rock or dust called meteors burning up in Earth's atmosphere. Most of them are no bigger than a single grain of sand. A grain of sand? But it looks so bright from all the way down here. That's because they are hitting our atmosphere at up to 160,000 miles per hour. The air violently compressing in front of the space rock creates a blazing hot trail of glowing air.

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So I've been wishing on flaming space dust. I still think that's pretty lucky. Alright Finn, time for the quiz. Are you ready? Okay, I'm ready. Hit me with those star facts.

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First question. What two gases make up most of a star? Next one. What is the name of the scientific effect that makes stars twinkle? Question three. Which star is the centre of our solar system? Here's number four. What is the name of the incredibly huge red hypergiant star we talked about? Last question. What explosive event happens when a massive star runs out of fuel and dies? Great job! Let's go through the answers. The answer to question one is hydrogen and helium. Our sun is about 73% hydrogen. For question two, it's called stellar scintillation. Earth's wobbly atmosphere bends the light. Number three, the answer is the sun. It's actually classified as a yellow dwarf star. Question four. The giant star is Stevenson two hundred eighteen, and it could easily swallow Saturn. And the final answer is a supernova, the biggest and brightest explosion in the galaxy.

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I got most of those. But my brain is still stuck on the fact that I have exploded star iron in my blood. That is the ultimate superhero origin story.

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It really is. Science gives us the best true stories ever. Next time you look up at the night sky, you'll know exactly the massive scale of what's happening up there.

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I'm definitely going to show off and yell Stellar Scintillation the next time I see a twinkling star.

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Do it! Hey everyone! If you loved exploring the stars with us today, please leave us a five-star review. Just scroll down on your podcast app and tap those five stars. Five stars for a show all about stars. It's the perfect match. And don't forget to check out our site, kidopoly.com. We've got tons of fun learning games and space activities waiting for you there.

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Yeah, and if you want to shout out on the show, or just want to say hi and tell us your favourite star fact, email us at hello at kidopoly.com.

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Keep looking up and stay curious. See you next time on Science Is Not Boring. Bye, Star Explorers!