[Curiosities] Why do the stars blink?

[Draeno]

 

Observing the sky flooded with brilliant stars is probably one of the favorite pleasures on clear nights. Of different luminosity, color or in different groupings, enjoying this free landscape is within everyone's reach. However, when you look up, there is a detail that is not overlooked: the stars are constantly blinking in the sky. Have you ever wondered what this phenomenon is due to? Are the stars really emitting light intermittently, or is it all just an optical effect?

DISPERSION FLICKER
To answer this question there are two things we need to take into account: the composition of our atmosphere and why the stars shine. The first is simple, since it is known that the layer that surrounds our planet is an accumulation of gases and particles in suspension, which are at different temperatures, concentrations and pressures depending on the study area. For the second, let's stay with the fact that the star pretends to be a large nuclear reactor; so that it is a thermonuclear fusion of helium inside that causes the release and irradiation of energy, part of it in the form of light.

Therefore, it seems unlikely that the flickering has its origin in this constant and intrinsic reaction to the star, and in turn, everything indicates that a changing and inhomogeneous atmosphere could be the cause of the flickering. And it is that, indeed, it is so: everything is due to an optical effect produced by the atmosphere itself.

In this way, the energy and light that is generated in the star constantly reaches the Earth's atmosphere. Now, when the particles that make up the light, the photons, enter the gas shell, they can collide with the scattered particles, completely altering the direction they are taking. In addition, changes in the magnitudes of pressure and temperature as they go deeper into it, can also bend their trajectory, deviating from linearity. These two effects cause that the deflected photons do not reach the eyes of the observers, giving rise to small periods where the light disappears. These are the famous flickers in the brightness of the stars.

DO THE PLANETS AND THE SUN BLINK?
The dispersion effect is more observable, and striking, in those astronomical objects that are at a greater distance. That is to say, the further away the star is, the amount of light that reaches the atmosphere is less, since there are more possibilities that energy has been lost along the way, in phenomena of dispersion and [CENSORED]ture of the trajectory when coming into contact with other cosmic materials. In nearby objects, the amount of light that arrives is much greater and, although some of it is scattered in the atmosphere, it does not affect the constancy and the flickering is not appreciated. This is what happens, for example, with the Sun: the closest star to planet Earth.

 

https://www.nationalgeographic.com.es/ciencia/por-que-parpadean-estrellas-cielo_19695