Twinkling of stars is primarily due to the atmospheric

The twinkling of stars, scientifically known as stellar scintillation, is primarily caused by the atmospheric refraction of starlight [1]. As starlight enters the Earth's atmosphere, it undergoes continuous refraction through layers of air with varying densities and a gradually changing refractive index [1]. Because the atmosphere is not stationary and physical conditions like temperature and density fluctuate, the apparent position and brightness of the star change slightly and rapidly [1]. This atmospheric turbulence distorts the incoming light, resulting in the perceived 'twinkling' effect. While planets shine steadily because they are closer and appear as extended sources, stars are distant point sources whose light path is easily deviated by these atmospheric shifts [1]. Other phenomena like reflection, polarization, and dispersion do not cause this specific temporal variation in stellar intensity [1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > Twinkling of stars > p. 168