Why does the light from stars / satellites tremble?

Question

Clear Sky.

1 ---> Light from stars visible.

2 ---> Light from satellites visible.

3 ---> Light from airplanes (passing by) visible.

Apart from the change in color, the light from 1 and 2 seems like its trembling but not 3.
Why is that so?

A word commonly used instead of “tremble” for this effect is “twinkle”, as in the song “Twinkle, Twinkle, Little Star”. — Todd Wilcox, Jul 29 '22 at 12:47
A less commonly used word in popular culture but used by astronomers is scintillation (visible light{ 1, 2 and radio 3) though that word is also used for light production by ionizing radiation in other contexts. Scintillation (disambiguation) — uhoh, Jul 29 '22 at 17:33
There's an interesting example video in What exactly causes "color twinkling" and why does it seem that any color might be furthest refracted for a moment? — uhoh, Jul 29 '22 at 17:34
@ToivoSäwén that is a great answer as well. Thank you. I should have checked better. So that's why during a hot summer day, when it's windy, the wind stops the photons from bumping onto my leg resulting me not experiencing hot temperature, right? — Engineer, Jul 29 '22 at 19:14

score 13 · Accepted Answer · edited Jul 29 '22 at 07:16

13

The light from stars comes through the atmosphere and gets distorted like light passing through a pool. Stars are particularly prone to this effect because they are single points and the light only follows one path to your eye.

Planets don't twinkle as much because they are tiny circles and the light from either edge of the planet travels slightly different paths to your eye.

So for a planet to twinkle multiple paths would have to be blocked at once which is less likely.

Satellites are also less prone to twinkling because they are not points. Planes on the other hand will never twinkle because they are large objects whose light doesn't even need to pass through the entire atmosphere.

edited Jul 29 '22 at 07:16

PM 2Ring

11,873

answered Jul 28 '22 at 23:36

shai horowitz

1,853

Thank you Shai. Is the distortion so little that the light seems continues? – Engineer Jul 29 '22 at 00:02
Also, the twinkling loop time seems way too long if we take into account the speed of light and the distance of the atmosphere. – Engineer Jul 29 '22 at 00:07
The trembling stopped now. Why ? – Engineer Jul 29 '22 at 00:58
The light travels through the atmosphere nearly instantly so if you can see the star or not is a description of the atmosphere at the given time rather then anything to do with the light of the star. the atmosphere varies in a continuous way so you see the light vary continuously. – shai horowitz Jul 29 '22 at 01:20
The trembling may have stopped because the atmosphere around where you are may be more calm now. – shai horowitz Jul 29 '22 at 01:20
1

Thank you! Have a great day! – Engineer Jul 29 '22 at 02:03

Why does the light from stars / satellites tremble?

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