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why do stars twinkle in the night sky

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.
Though light pollution has made the night sky harder than ever to observe, a clear and dark evening can reveal to the eye roughly 2,500 twinkling stars, The Atlantic. (There may be a septillion stars in the observable universe, but far fewer are visible to the naked human eye. ) There are few proofs as convincing as this a sky crowded with flickering constellations of the vastness of the universe.


But even the stars signature twinkle signals something much greater. The closest star in the, beyond our own, is Proxima Centauri, a cool from the sun. One of the farthest visible, the Andromeda galaxy, is more than 14 quintillion miles away that's a staggering 14 million trillions. Because it has traveled from such great a distance, the starlight that reaches Earths surface is little more than a spindly thread. But that light does not waver. Starlight shines straight and true. (That is, barring some long-ago celestial event only visible to us now. ) is a result of these thin but steady strands of light hitting the Earths atmosphere and bouncing around: reflected by airborne particles here, scattered by gas molecules there. Because starlights path is so narrow having traveled from so far away its easy to see these minor deviations. Planets, on the other hand, shine steadily in the night sky as seen from Earths surface. Thats because they are so much closer to us, and the light has a much shorter distance to travel.


The light reflected off planets (whereas stars generate their own) has a much wider path than that of starlight. When you look at a planet through a telescope, you see a solid sphere. When you look at stars through a telescope, all you see are pinpricks. (Their light has traveled too far for telescopes to make much difference. ) And because the course of the light is broader, its harder to see how the light reflected off of planets is jostled around by Earths atmosphere. From space, stars shine and planets reflect without interruption, meaning twinkling night stars are a phenomenon best experienced from Earth preferably from an, where light pollution has yet to cloud those beautiful, glittering skies. Stargazing hotspots and are mostly far-flung. Chile's Atacama Desert, for example, with its high altitudes and dry, non-polar air, has become a booming destination for astro-tourism. Of course, there are more accessible options, including Cherry Springs State Park in Pennsylvania and (the 13,796-foot summit can be reached by car). But there are few places on Earth where you can better experience the magic of thousands of twinkling little stars piercing the night sky.

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