Bad Astronomy: Misconceptions and Misuses Revealed, from ...

9
PPPPPP
Twinkle, Twinkle, Little Star:
Why Stars Appear to Twinkle
I was
“Twinkle, twinkle, little star, how I wonder what you are.”
— Lyrics by Jane Taylor,
music by Wolfgang Amadeus Mozart
“Twinkle twinkle, little planet, can’t observe so better can it.”
— The Bad Astronomer
sitting at the observatory, waiting. It was 1990, and I was
trying to make some observations as part of my master’s degree
work. The problem was the rain. It had poured that afternoon (not
unusual for September in the mountains of Virginia), and I was
waiting for the sky to clear up enough to actually get some good
images.
After a few hours my luck changed, and the clouds broke up.
Working quickly, I found a bright star and aimed the telescope
there to focus on it. But try as I might, the image of the star on the
computer screen never sharpened. I would move the focus in and
out, trying everything, but no matter what I did the star image was
hugely fuzzy.
So, I did what any astronomer locked in a small, dark room
for three hours would do. I went outside and looked up.
The bright star I had chosen was high in the sky and twinkling
madly. As I watched, it flashed spastically, sometimes even changing
89