Passion Blog Week 3- Twinkle, Twinkle…

As long as you didn’t grow up in the middle of New York City, you’ve probably seen stars before.  Even if you did grow up there, you’ve probably caught yourself singing “Twinkle, Twinkle, Little Star…” at some point.  However, have you ever stopped to think about why that little star is twinkling?  Surely stars don’t just turn on and off- if they did, trying to walk during the day when the sun was winking constantly would be a real pain.  The answer is actually quite complicated.
Imagine being outside on a hot day on a pavement-covered parking lot.  You look straight ahead, and everything in front of you is blurry.  You can see heat waves rising off the ground.   Everything behind them is distorted.  Stars twinkle for the exact same reason.  At night, the atmosphere cools down and the earth is still warm.  Heat rises, which causes stars behind the waves to twinkle.   In astronomy, this is referred to as “atmospheric scintillation”- or just twinkling stars.   However, there is a cool part to this.  Stars twinkle in odd ways- you may have noticed some that even appear to change colors.  This is because the atmosphere is like a prism that divides up light into colors.  I tried an experiment a few years ago with this.  I pointed my telescope at the star Sirius, tapped the tube, and took a picture.  Pretty nifty, huh?
However, twinkly stars can actually be a bit of a pain.  That generally means that the atmosphere is unstable and blurs pictures of planets, too.  Or the moon.  The random blurs and stuff are caused by the same thing that makes stars twinkle.   That’s one of the reasons it’s so hard to take pictures of planets- they appear to be constantly moving because of our atmosphere.