Our Immaculate Misconceptions feature sees writer Kathryn Egerton, destroying our childhood nursery rhymes.
No, stars do not twinkle – we’re all living a lie.
Twinkle, twinkle, little star, how I wonder what you are. A well known nursery rhyme, but when you look closer is it actually correct? Well, here comes science to ruin the rhyming couplets of our childhood, because the truth is, stars don’t actually twinkle.
It’s pretty simple when you think about it, what with stars being giant exploding balls of gas burning constantly for millions of years, the idea that the light emitted from stars flickers on and off is a blindingly obviously lie.
Despite this, when you gaze up at the night sky, perhaps with a bf/gf or, like me, with your mum, you will see twinkling dots and these will, most of the time, be stars.
But, what’s important is that its not the stars that twinkle. What you’re seeing is the result of light from stars moving toward earth though our tricky atmosphere, a
journey which results in “scintillation”
Scintillation, which we know as star twinkling, is the result of the 
earth’s
atmosphere interfering with the rays of light given out by the star. Each
temperature zone in our atmosphere is like a bubble of warmer or cooler air. These pockets of air diffract (bend) any light rays moving through them in the same way that light is diffracted by hot air above a warm road on a summers day to give a mirage effect. This refraction will happen when any rays of light from space (not just from stars) pass through the earth’s
atmosphere.
You may have heard “stars twinkle, planets shine”. So why do only stars appear to twinkle? Its all to do with
scintillation and the fact that planets within our own solar system are much closer to Earth than stars.
Stars are so far away that they appear as dimensionless points to those viewing from Earth, so the rays of light reach our eyes in a very narrow beam. This thin beam is diffracted as it passes through each atmospheric
temperature zone so that the star’s image appears to shift as we observe it.
Planets, on the other hand, can be seen as disks because of how much closer they are to us. Therefore, a much thicker bundle of light reaches us. Atmospheric shifts will cause bending or “twinkling” of any of the rays coming from a planet but these numerous points average each other out so planet twinkling is much less noticeable than in stars. Interestingly, if you looked out into space from the moon, you wouldn’t see stars twinkling at all.
So there you have it. Stars themselves don’t actually twinkle. But I admit “twinkle, twinkle, little dimensionless point of starlight..” probably wouldn’t have made for a great nursery rhyme.
Kathryn Egerton
Check out more of our Immaculate Misconceptions!