To distinguish with the naked eye fixed star from the planet very easily: the planets Shine calm light, stars same twinkle. And the bright star just above the horizon and shimmer in different colors. Particularly strong and colorful stars twinkle in the frosty nights and windy weather and after rain, when the sky quickly cleared of clouds.
The flickering is not a property inherent to the stars. If we look at the stars in outer space where there is no atmosphere, we will not notice the twinkling of the stars: they Shine there quiet, constant light. The reason for the flicker is the earth's atmosphere, through which the rays of the stars must go through before reaching the eye. About the same happens when on hot days the soil is strongly heated by the Sun. The star light in this case we have to permeate not homogeneous environment, and gas layers of different temperature, different density, and hence different prelomlyalas.
The light rays undergo numerous deviations from the straight path, focusing, then dissipating. Hence the frequent changes in the brightness of the stars. As well as refraction is accompanied by svetorasseyanie, along with fluctuations in the observed brightness and color changes.
Why the planet, unlike stars, do not twinkle and Shine smoothly, quietly? The planet is much closer to us than the stars. Therefore, they are presented to the eye is not the point, and a luminous circle, disk, although such small angular sizes, due to their blinding brightness these angular dimensions are almost imperceptible.
Every point of this circle flickers, but changes the brightness and color of individual pixels are independently of one another, in different moments of time, and therefore compensate each other; the weakening of the brightness of a single point coincides with the increased brightness of the other, so that the total light power of the planet remains unchanged. Here is a quiet, flicker-free Shine planets.
That is, the planets seem to us to be flicker-free because twinkle in many points, but at different points in time.