why do stars twinkle but not planets

Stars twinkle, while planets (usually) shine steadily. Why? Stars twinkle because theyre so far away from Earth that, even through large telescopes, they appear only as pinpoints. And its easy for Earths atmosphere to disturb the pinpoint light of a star. As a stars light pierces our atmosphere, each single stream of starlight is refracted caused to change direction, slightly by the various temperature and density layers in Earths atmosphere. You might think of it as the light traveling a zig-zag path to our eyes, instead of the straight path the light would travel if Earth didnt have an atmosphere.

Planets shine more steadily because theyre closer to Earth and so appear not as pinpoints, but as tiny disks in our sky. Youd could see planets as disks if you looked through a telescope, while stars would remain pinpoints. The light from these little disks is also refracted by Earths atmosphere, as it travels toward our eyes. But while the light from one edge of a planets disk might be forced to zig one way light from the opposite edge of the disk might be zagging in an opposite way. The zigs and zags of light from a planetary disk cancel each other out, and thats why planets appear to shine steadily.

You might see planets twinkling if you spot them low in the sky. Thats because, in the direction of any horizon, youre looking through more atmosphere than when you look overhead. If you could see stars and planets from outer space, both would shine steadily. Thered be no atmosphere to disturb the steady streaming of their light. Can you figure out which objects are stars and which are planets just by looking for the twinklers vs the non-twinklers? Experienced observers often can, but, at first, if you can recognize a planet in some other way, you might notice the steadiness of its light by contrasting it to a nearby star.

Bottom line: Stars twinkle because they appear as tiny pinpoints as seen from Earth, even through telescopes. Planets dont twinkle because they are closer, and thus appear larger in our sky, as tiny disks instead of pinpoints.
Everyone must be familiar with the famous poem : Twinkle Twinkle Little Star. Well, its not just a poem for children, its actually referring to a particular scientific phenomenon that has fascinated observers from many years. They certainly appear to do so, Why do all the other stars in the night sky appear to twinkle, but Planet s never does?

Why Do Stars Twinkle? Light from stars crosses a very long distance to reach us and also passes through Earths atmosphere, which vary in temperature and density. Our atmosphere is very turbulent, with streams and eddies forming, churning around, and dispersing all the time. Every layer of Earths atmosphere has air moving in different directions at different intensities. When light from stars passes through the atmosphere, it is bent due to refraction, which is why stars seem to twinkle when we stare at them. If viewed from outer space, you would not see the stars twinkling.

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