Why do stars twinkle?
We earthly observers have the impression that the stars twinkle, but in fact the stars themselves cannot twinkle. But why do we think so? Because we see the light from the stars after it has passed through the thickness of the atmosphere. This is an indispensable condition for flickering. If you observe even a very distant star from space, then it will not flicker. Astronauts observing the stars from the moon, where there is no atmosphere, saw a sky dotted with stars that shone with a steady, unblinking light. But on Earth, covered with a thick "blanket" of the atmosphere, the rays of light from stars, before reaching the surface, are repeatedly refracted in different directions. The masses of air around us do not stand still, they are constantly moving relative to each other: warm air rises, cold air descends. Air refracts light differently depending on temperature. When light passes from a layer of air of lower density to a layer of higher density, the flickering of light begins. At the same time, the outlines of the stars become blurry, their images increase. The intensity of the radiation of stars, that is, their brightness, changes. Now the star is visible very well, then it has dimmed ...
However, not all luminaries in the night sky flicker.
For example, the planets Venus and Mars do not flicker.
Why?
Even the ancients noticed that there are objects in the sky that are unlike others.
Five luminous points move among the stars and differ from them in even light.
These are the five planets visible to the naked eye: Mercury, Venus, Mars, Jupiter, Saturn.
The planets of the solar system are not so far removed from the Earth compared to the stars, they are our closest neighbors.
We see them as discs, not as flickering dots. In fact, they also twinkle, but this twinkling does not occur at one point, as in distant stars, the light of which reaches us in the form of a beam, but over the entire surface.
As a result, we perceive the glow of the planets as even.
This is interesting!
Stars have such a powerful glow, overcoming great distances, because they are constantly undergoing thermonuclear reactions. Planets are solid bodies, they do not emit light on their own, but only reflect the light that comes from the star around which they revolve.
