Why do stars twinkle?

The Tweeting the Universe authors on what makes stars sparkle

‘Twinkle, twinkle, little star, how I wonder what you are. Up above the world so high, like a diamond in the sky,’ wrote Jane Taylor in 1806.

Ancient people noticed that stars twinkle whereas planets do not. They also noticed stars appear fixed to firmament whereas planets wander.

Both phenomena are explained by distance. Stars are so immensely far away that they appear pinpricks and their movement is unnoticeable . . .

. . . Planets, on the other hand, are relatively nearby so they appear as tiny discs in a telescope, and their movement across sky is marked.

Looking up through turbulent atmosphere at stars & planets is like looking at lights on a swimming pool ceiling from bottom of pool.

Wavering of water makes point-like lights jitter back/forth (twinkle). But bigger lights merely ripples around edges, so stays steady.


Tweeting the Universe by Marcus Chown and Govert Schilling is published by Faber.