The perception of stars moving fast in the night sky is typically an optical illusion known as "the twinkling of stars" or "stellar scintillation." Several factors contribute to this phenomenon:
Atmospheric Turbulence: Earth's atmosphere is not completely still; it contains layers of constantly moving air. When starlight passes through these turbulent layers, it gets refracted or bent, causing the apparent position of the star to shift slightly. This refraction can give the impression of stars rapidly moving or twinkling.
Light Path Variations: As starlight passes through different layers of the atmosphere with varying densities, temperatures, and moisture content, its path gets bent in different directions. This bending causes the apparent position of the star to fluctuate, creating the perception of fast movement.
Eye Sensitivity: The human eye is more sensitive to changes in bright objects than to steady lights. When a star's light rapidly fluctuates due to atmospheric turbulence, our eyes interpret it as quick movements rather than a continuous source of light.
It's worth noting that planets, such as Venus or Mars, appear relatively steady compared to stars. This is because they are closer to Earth and their light passes through a larger portion of the atmosphere, minimizing the effects of atmospheric turbulence.
Additionally, stars near the horizon can appear to move more than those directly overhead due to a longer path through the atmosphere, resulting in more pronounced twinkling.
While this twinkling effect can be captivating, it is an atmospheric phenomenon rather than actual movement of the stars themselves.