The planets don’t twinkle because they are much closer to Earth and are seen as extended sources of light. Unlike stars, which are viewed as point-sized sources, planets can be considered as collections of a large number of point-sized sources.
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Planets do not twinkle like stars because they exhibit a noticeable disk size, unlike the point-like appearance of stars. The larger apparent size of planets makes them act as extended light sources, minimizing the effects of atmospheric turbulence on their brightness. Unlike stars, whose light is concentrated into a single point, the scattered light from the larger planetary disks tends to average out the atmospheric fluctuations. This results in a steadier, less twinkling appearance for planets. The apparent disk of planets acts as a stabilizing factor, reducing the impact of atmospheric refraction and providing a more constant illumination when observed from Earth.