Why do stars twinkle more near the horizon?
Quick Answer
Near the horizon, starlight passes through more turbulent atmosphere, which bends the light more unpredictably. That makes the star’s brightness and position seem to shimmer.
The Full Story
Twinkling, or atmospheric scintillation, happens because Earth’s atmosphere is constantly moving and changing in density. As starlight travels through these shifting layers, it is refracted slightly in different directions, so the star appears to flicker. Near the horizon, the light must pass through a thicker slice of atmosphere, so the effect is stronger. Planets usually twinkle less because they appear as tiny disks rather than point sources. This is why ground-based observatories often use adaptive optics or are placed on high, dry mountaintops.
Key Facts
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