Stars twinkle because their light passes through the Earth's atmosphere, where it is continuously refracted due to varying densities and temperatures in the air layers. This causes the apparent position and brightness of the star to fluctuate rapidly, making it appear to twinkle to an observer on Earth.
Explanation of Twinkling
- Starlight travels vast distances and appears as point sources of light.
- When starlight enters Earth's atmosphere, it passes through layers with different optical densities.
- These varying densities bend (refract) the light rays several times as the atmosphere moves and changes.
- The continuous shifting of the refracted light causes changes in the star's apparent position and intensity, resulting in the twinkling effect.
Why Only Stars Twinkle, Not Planets
- Stars are very far and appear as point sources.
- Planets being closer appear as tiny disks, not points.
- Light from planets comes from multiple points on the disk, and the atmospheric refraction effects cancel out.
- Hence, planets shine steadily without twinkling.
In summary, twinkling is due to atmospheric refraction of starlight, caused by continuously changing air layers bending the light in varying ways as it reaches the observer on Earth.
