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Why Do Stars Twinkle? | Amazing space facts for kids · The Curious Kidcast | Fun Facts and Curious Questions

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  Twinkle, twinkle, little star. It's a nursery rhyme we all know
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  well, but ever wondered what actually makes a star twinkle?
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  Today we are solving a mystery that has been confusing humans
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  for thousands of years, and the answer involves air, light,
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  invisible forces, and a star that has been mistaken for a UFO
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  so many times it practically deserves its own government
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  file. This is the Curious Kid cast.
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  Curious kid cast? Here we go.
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  Questions poppin. Minds will blow Big ideas.
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  They're taking flight. Let's explore.
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  Feel the light. Welcome to the Curious Kid Cast,
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  the podcast where we take the questions rattling around inside
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  your brain, the ones your teacher probably said were a bit
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  off topic, and we answer them properly with real science,
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  absolutely terrible jokes, and strictly no homework.
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  I'm Charlie and if you have ever looked up at the night sky and
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  thought hang on, are the stars winking at me, then buckle up
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  because today we find out why. Now today's question came from a
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  kid called Reuben who lives in Edinburgh.
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  Reuben was out in the garden one night with his Gran who was
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  trying to show him some constellations on a star
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  spotting app. But Reuben stopped paying
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  attention to the app because he noticed one star near the
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  horizon that was flashing red, then blue, then white over and
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  over again like it had its own little disco going on.
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  Reuben turned to his Gran and said very seriously, Gran, I
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  think that star is broken. His Gran had absolutely no idea
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  what to say. So Reuben, being an extremely
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  sensible person, sent his question to us.
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  Reuben, this episode is entirely your fault and we are very
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  grateful. So why do stars twinkle?
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  Here is the part that is going to mess with your head a little
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  bit. Stars are not actually twinkling
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  at all. The stars themselves are just
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  sitting out there in space, being enormous and on fire,
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  glowing away perfectly, steadily, minding their own
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  business. They are not blinking.
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  They are not winking. They are not doing a little
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  sparkle dance for your entertainment.
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  The twinkling is happening right here above your head, and the
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  culprit is something you cannot even see.
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  Air Earth is wrapped in a thick blanket of air called the
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  atmosphere, and this atmosphere is not sitting still like a nice
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  calm bath. It is full of different layers,
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  some warm, some cold, some swirling around in huge
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  invisible currents, all bumping into each other constantly.
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  And all of that movement causes light to bend.
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  Scientists call this atmospheric scintillation, which sounds like
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  something a wizard would shout before casting a spell.
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  And honestly, I think it should be atmospheric scintillation.
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  Nothing happens, it just sounds extremely impressive at dinner.
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  Here is a brilliant way to picture what is going on.
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  Imagine a coin sitting at the bottom of a swimming pool when
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  the water is perfectly still. The coin looks nice and clear,
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  but the moment someone does a massive bomb dive into the pool
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  and the water starts rippling and wobbling everywhere, the
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  coin looks like it is jumping around and flickering and
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  possibly trying to escape. The coin has not moved a single
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  millimetre. The water is just messing with
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  how you see it. Earth's atmosphere does exactly
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  the same thing to Starlight. As the light travels down
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  through all those layers of moving air, it gets bent and
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  bounced around, and by the time it reaches your eyes it seems to
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  be flickering. The star is innocent, the air is
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  the 1 causing chaos. One big reason stars twinkle so
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  dramatically is that they are almost impossibly far away.
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  Even though stars are often absolutely enormous, way bigger
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  than Earth, they are so distant that they look like tiny
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  pinpoints of light to us. And a tiny pinpoint of light is
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  very, very easy for the atmosphere to mess around with.
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  It is a bit like trying to keep a laser pointer perfectly still
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  while someone is aggressively tickling you.
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  Any tiny wobble in the air and the star seems to jump and
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  flash. If the beam of light were wider,
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  the wobble would matter less, but for stars, every little
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  tremor in the air makes a big difference.
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  Here's another brilliant fact to impress people with.
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  Stars near the horizon twinkle way more than stars high
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  overhead. When a star is low in the sky,
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  it's light has to travel through much more atmosphere to reach
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  you. Like the difference between
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  walking through a short corridor and a very long one where
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  someone keeps bumping into you every two seconds.
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  More atmosphere means more bending, more wobbling and more
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  twinkling. O.
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  If you want maximum twinkle, look near the horizon.
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  If you want a calmer star, look almost straight.
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  U. You are basically a scientist
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  now. Now remember Reuben's star, the
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  one flashing red and blue and white like a tiny space disco?
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  That is a real thing, and here is why it happens.
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  Different colours of light bend by slightly different amounts
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  when they pass through air. So when the atmosphere is
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  especially turbulent and wobbly, it can separate out those
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  different colours and fire them at your eye at slightly
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  different moments. Red one instant, blue the next,
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  white after that and then maybe a bit of green just to keep
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  things interesting. It looks absolutely wild and it
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  is completely real. The star that does this most
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  dramatically is called Sirius. Sirius is the brightest star in
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  the entire night sky, which means when it gets near the
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  horizon it goes absolutely full theatrical mode, flashing
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  colours, flickering like mad, putting on a complete
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  performance. In fact, people have actually
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  called the police reporting a UFO because Sirius was putting
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  on such a dramatic light show near the horizon that they were
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  completely convinced I think alien was going on.
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  That is not me making it up, it has happened multiple times.
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  Sirius is not a UFO, it is just a star with no chill whatsoever.
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  Here is a fact that will make your brain feel slightly
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  strange. Sirius is about 8.5 light years
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  from Earth. Now a light year sounds like a
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  measurement of time, but it is actually a measurement of
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  distance. One light year is how far light
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  travels in a whole year. And since light moves at about
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  300,000 kilometres per second, one light year is roughly 9.46
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  trillion kilometres trillion. That is A1 with 12 zeros after
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  it. So when you look at Sirius, you
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  are not seeing it as it looks right now, you are seeing light
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  that left it 8.5 years ago. You are looking into the past.
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  The night sky is basically a time machine, and nobody
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  mentions this nearly enough, right?
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  Here comes the bit that is genuinely useful.
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  It's a sleepover or camping trip.
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  Do planets twinkle too? The answer is yes sometimes, but
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  usually much less than stars. And here is the genius part.
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  You can actually use this to tell the difference between a
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  planet and a star with just your eyeballs.
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  If you spot a bright object in the sky that barely flickers at
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  all, there is a decent chance it might be a planet like Venus or
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  Jupiter, not a star. Why do planets stay steadier?
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  Because they are much closer to Earth than stars are, and
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  because they are closer, they appear as very tiny discs rather
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  than single sharp pinpoints, even though your eyes cannot
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  quite see the disc shape without a telescope.
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  Because the planets light is spread out just a tiny bit more,
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  the atmospheres wobbly effects kind of average out and cancel
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  each other. It is a bit like how it is
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  easier to balance a wide flat tray than a tiny little marble.
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  One is spread out enough to handle the wobble, the other
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  gets thrown about all over the place.
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  That said, planets can still twinkle when they are very low
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  in the sky or when the atmosphere is being particularly
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  dramatic. So it is not perfect as a test,
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  but it is a brilliant starting point.
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  Steady glow could be a planet flickering and flashing like a
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  broken Christmas light. Almost certainly a * Get
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  yourself outside on a clear night and try it.
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  You will genuinely feel like a wizard.
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  Now, here is something interesting about looking at
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  stars from space. If you were floating in a
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  spacecraft above Earth's atmosphere, looking out the
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  window, stars would barely twinkle at all.
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  Without the air getting in the way, their light would arrive
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  much more steadily. This is a big reason why space
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  telescopes take such incredibly sharp photos of the universe.
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  They are not fighting through all that turbulent air.
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  It is also why many of the biggest telescopes on Earth are
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  built on top of very tall mountains where the atmosphere
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  above them is thinner and calmer and the stars wobble less.
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  For scientists working on the ground, there is a brilliant
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  piece of technology called adaptive optics.
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  These are telescope mirrors that can physically change shape
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  dozens of times per second to correct for the atmosphere's
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  wobbling in real time. Imagine trying to draw a
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  perfectly straight line while someone is constantly shaking
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  your desk, but you have a magic pen that automatically adjusts
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  itself to keep the line straight every single instant.
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  That is basically what adaptive optics does, and it means ground
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  based telescopes can still get astonishing views of the
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  universe even through wobbly air.
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  Here are a few extra star facts that are worth knowing just
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  because they are genuinely great.
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  Stars are not all the same colour, and their real colour
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  tells you how hot they are. Blue stars are the hottest, red
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  stars are cooler, yellow and white stars are somewhere in
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  between. Our sun is a yellow White Star,
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  which makes it fairly average and middle of the road in Star
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  terms. The sun, the giant burning ball
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  of fire that keeps all life on Earth alive, is considered
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  pretty normal. Stars are wild.
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  Also, many stars are between 1 and 10 billion years old.
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  Some are nearly as old as the universe itself.
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  The lights you see twinkling tonight have been burning for
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  longer than our entire planet has existed, which is one of
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  those facts that makes you stare into the distance for a while.
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  So here is your challenge for the next clear night.
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  Go outside and find a bright object near the horizon.
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  Watch it for a few seconds. Is it flickering like mad?
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  Is it flashing colours? Star.
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  Now look for a bright object higher in the sky that barely
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  moves or flickers. That might be a planet.
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  You have just used actual astronomy to read the actual
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  sky, and you did not need a single piece of equipment to do
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  it. Just eyes, knowledge, and
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  hopefully a coat because it is probably cold.
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  So why do stars twinkle? Because their light has to
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  travel through Earth's restless, swirling, turbulent atmosphere
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  before it reaches your eyes, and all that moving air bends the
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  light around, making the star seem to flicker.
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  The star is not winking at you, but now that you know the truth,
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  you can absolutely wink back before we do the quiz.
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  If you have enjoyed this episode, please share it with a
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  friend, a sibling, A classmate, or any adult who asked a
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  question and did not know the answer.
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  It really helps us reach more curious kids around the world.
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  And if you have got a question you want me to investigate on
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  the show, go to curiouskidcast.com and send it
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  in. Your question could be the next
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  episode, and if it involves anything exploding or Catching
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  Fire, we will do our absolute best right then.
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  Quiz Time 3 Questions No looking things up, no asking a parent on
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  your own. Let's find out what you have
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  learned. Question One Stars appear to
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  twinkle because of what is it? A the star is switching its
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  light on and off like a lamp. B Earth's atmosphere keeps
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  bending the Starlight as the air moves around, or C tiny clouds
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  are passing in front of the star really fast.
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  The answer is B. Earth's atmosphere bends the
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  Starlight as it moves around. The star is doing absolutely
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  nothing unusual. It is our wobbly air that is
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  causing all the drama. The star is innocent and the
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  atmosphere needs to have a word with itself.
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  Question 2. Why do planets usually twinkle
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  less than stars? Is it a Planets are made of
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  different materials, so they glow more steadily.
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  B planets are closer to Earth so their light appears as a tiny
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  disc rather than a single sharp pinpoint, or C planets are
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  colder and cold things do not twinkle.
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  The answer is B. Because planets are closer,
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  their light reaches us as a slightly broader patch, and the
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  atmosphere's wobbles average out more.
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  The disk shape is the secret option.
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  C was absolutely not a real scientific fact and if you
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  picked it that is fine. But also cold things can
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  definitely twinkle. Ask an ice cube near a candle.
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  Question 3. Which star is the brightest in
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  the night sky, flashes different colours near the horizon, and
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  has been reported to the police as a UFO multiple times.
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  Is it a Polaris, also known as the North Star, B Beetlejuice,
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  which is also fun to say out loud three times, or C Sirius,
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  also known as the Dog Star? The answer is C Sirius, the most
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  dramatic star in the sky, confirmed.
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  It has been causing confusion, wonder and entirely unnecessary
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  police phone calls for centuries, and honestly, we
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  respect it enormously for that. And that is a wrap on today's
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  episode of The Curious Kid cast. A massive thank you to Reuben
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  from Edinburgh for a genuinely brilliant question.
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  The answer was floating above your head the whole time, which
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  is either very satisfying or slightly annoying, and both
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  reactions are completely valid. I'm Charlie.
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  This has been the Curious Kid cast.
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  Keep asking questions, keep looking up, and remember, every
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  time you see a star twinkling tonight, you are watching light
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  that left its source years ago, crossed trillions of kilometres
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  of empty space, survived the entire journey across the
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  universe, and then got absolutely wobbled by our
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  atmosphere right at the very last second.
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  It came all that way. Hey, we'll let.
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  Your questions rise. Lift them up to the endless sky.
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  Every. Why is as far so bright?
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  Curious Kid cast Ignite the Light.