Stars twinkle, but planets don't?

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SUMMARY

Stars twinkle due to atmospheric conditions, specifically variations in temperature and pressure that affect the refractive index of light. This causes a shifting image of the observed stars. In contrast, planets do not exhibit the same twinkling effect primarily because they are not point sources; they have a discernible size, which stabilizes their appearance despite atmospheric disturbances. The brightness of an object does not influence this phenomenon, as some stars can shine brighter than planets at times.

PREREQUISITES
  • Understanding of atmospheric optics
  • Basic knowledge of light refraction
  • Familiarity with celestial objects and their characteristics
  • Concept of point sources vs. extended sources
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  • Explore the differences between point sources and extended sources in astronomy
  • Learn about the brightness and visibility of celestial objects
  • Investigate the conditions under which planets may appear to twinkle
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Astronomy enthusiasts, educators, and anyone interested in understanding the visual phenomena of celestial objects and their behavior in Earth's atmosphere.

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Hello everyone - newbie here. Am I right to say that stars twinkle because of regions of the atmosphere being at different (and varying) temperatures and pressures etc., giving rise to a variation in refractive index and consequently a shifting image of the observed object? If so, why don't I observe planets to do the same thing? I thought it might be because planets appear much brighter, but then don't some stars shine more brightly than some planets at times? Thanks.
 
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Stars twinkle because of the movement and different temperatures in the atmosphere cause the light to refract. You have that part right, the reason that planets do not seem to twinkle (I have seen Saturn twinkle when close too the horizon) is not due to the brightness but it is due to the size of the image. Stars are point sources and planets have some size too them.
 

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