Stars Twinkle; Planets Do Not
To twinkle is to shine with a flickering light. The reason stars twinkle and planets do not is a useful piece of stargazing.
To twinkle is to shine with an unsteady flickering light. The cause is the atmosphere, not the star: pockets of air at different temperatures bend the light on its way down. Stars are so distant that they arrive as single points and flicker; planets show a tiny disc, and the flickers average out — which is how to tell them apart by eye.
- To shine unsteadily. *Stars twinkled overhead.*
- To sparkle with amusement. *His eyes twinkled.*
- In the twinkling of an eye — instantly. *Gone in the twinkling of an eye.*
Word forms
| Form | Word | Example |
|---|---|---|
| Verb | twinkle | The lights twinkle. |
| Past | twinkled | Twinkled faintly. |
| Noun | twinkle | A twinkle of amusement. |
| Adjective | twinkling | Twinkling lights. |
| Related | scintillation | Atmospheric scintillation. |
How it is used in a sentence
- Stars twinkle most near the horizon.More atmosphere to look through.
- Planets shine steadily.The observer's test.
- She had a twinkle in her eye.Amusement.
Stargazing basics
- Scintillation — the technical name for twinkling
- Seeing — how steady the atmosphere is on a given night
- Averted vision — looking slightly aside to see faint objects
- Light pollution — the main obstacle for most observers
- Dark adaptation — twenty minutes or more for the eye to adjust
From Old English *twinclian*, a frequentative form meaning to blink or wink repeatedly. The *-le* ending marks repetition, as in *sparkle* and *crackle*.
Why do planets not twinkle?
Because they show a small disc rather than a point. The atmospheric distortions across that disc average out, so the light stays steady.
Why do stars twinkle more near the horizon?
Because light from low in the sky passes through much more atmosphere before reaching your eye.