You all know the nursery rhyme. In fact, I’ll bet that most of you are humming it in your head right now after reading the title of this article. It’s cute, it’s easy for little ones to remember, and it asks an age-old, thought-provoking question.

“How I wonder what you are!”

OK, so it’s more of an exclamation than a question, but the question’s in there. It’s a thought mankind has pondered over all the years of our inhabitance of this wad of mud. It’s a big question – bigger than I can cover in this brief piece. I can, however, address one of the many fascinating things about stars. Why do they twinkle? What is it about them that inspired poet Jane Taylor to write a nursery rhyme about this twinkly trait of stars back in 1806? She certainly saw them twinkle, but I’m not sure if she ever really thought about the science behind that visual virtue of our celestial sky-denizens.

The scientific answer is defined by a term known as astronomical scintillation. That’s an interesting word, “scintillation.” (“Astronomical” is pretty interesting also, but I think we’re all pretty clear on what that means.) What does it mean if something is scintillating? I don’t know about you, but I’ve heard vapid conversations on TV like this all my life, usually with regard to some celebrity or another:

Airhead 1: “My, did you see the gown Suzy Starlet wore to the gala? It was simply scintillating!”
Airhead 2: “Oh, my stars, you are right. Suzy’s such a scintillating personality on her own, but that gown!”
Airhead 1: “And who was that on her arm but none other than Todd Tophat! His smile is just scintillating!”
Airhead 2: “Scintillation all around!”

Now it just sounds dumb, right? Well, if something is “scintillating”, it grabs your attention due to flashiness or brilliance. People who are enamored with movie stars or other celebrities may find them flashy or even brilliant at times. I think it’s interesting that a term applied to earthly “stars” is something that is scientifically used to describe real stars. Maybe that’s why we call celebrities “stars”. I’ll let you research that on your own.

Here’s another tidbit before I get to what atmospheric scintillation actually is. Plug that word into a thesaurus online or thumb through that old dog-eared copy of Roget’s Thesaurus you have on your bookshelf. Interesting. One of the common synonyms is “twinkle.” Yep. Twinkle. Of course, the song would be very difficult to sing if we sang, “Atmospheric scintillation little star …” Preschoolers would cry and throw Play-Doh at you for trying to get them to sing a song like that.

So, what is this twinkling effect, and more puzzlingly, why is it reserved for stars? Planets don’t twinkle, after all. What’s so special about stars?

It turns out that the twinkling is a result of two things – our atmosphere and the vast distances between us and stars. Starlight appears as a small pinpoint of light, even through a telescope. As that light passes through the atmosphere, it travels through tiny pockets of air with differing shapes, sizes and temperatures. These pockets act as lenses that distort and diffract the light, making it appear to vary rapidly with regard to brightness and position. Twinkle, twinkle.

Why doesn’t this happen with planets? If you spot an easily identifiable planet, like Venus, in the night sky, it looks like a bright, steadily burning light. It’s still a dot, but if you look closely (or through a telescope) you will see that it looks like a bright, defined disk. Planets are much closer to us than stars. That means we can discern their actual disc-like shape. They’re not just amorphous dots. Also, they appear much larger in our night sky (even though they are actually much smaller) than stars. They are so large, in fact, that their size eclipses the size of the lens-like pockets of air responsible for diffracting starlight.

There you have it. You now know why stars twinkle and planets don’t. It’s a good thing planets lack the scintillation of stars – for two reasons. One, it would sound weird to refer to actors, athletes, and musicians as “planets”. What if you heard this on New Year’s Eve?

“Welcome to a planet-studded night of music and entertainment as we count down to the new year. Join us for a great show planeting Ryan Seacrest!” Planeting? No, that’s not even a word. Maybe it would be if planets were more scintillating.

This article was written by Tilmer Wright, Jr. Tilmer is an IT professional with over thirty years of experience wrestling with technology and a proud member of the Authors Guild of Tennessee. In his spare time, he writes books.

You can find links to Tilmer’s books at the following location: https://www.amazon.com/Tilmer-Wright/e/B00DVKGG4K?ref=sr_ntt_srch_lnk_1…

His author information web site is here: http://www.tilmerwrightjr.com/

Credit for image accompanying this article: Acerview54 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0) No modifications made.