why do stars twinkle but planets don't?

Answer 1

Stars twinkle because of turbulence in the atmosphere of the Earth. As the atmosphere churns, the light from the star is refracted in different directions. This causes the star's image to change slightly in brightness and position, hence "twinkle." This is one of the reasons the Hubble telescope is so successful: in space, there is no atmosphere to make the stars twinkle, allowing a much better image to be obtained.


Planets do not twinkle the way stars do. In fact, this is a good way of figuring out if a particular object you see in the sky is a planet or a star. The reason is that stars are so far away that they are essentially points of light on the sky, while planets actually have finite size. The size of a planet on the sky in a sense "averages out" the turbulent effects of the atmosphere, presenting a relatively stable image to the eye.

Answer 2

The twinkling is caused by atmospheric refraction. Variations in atmospheric density bend light ever so slightly. This is the same phenomenon that makes things look wiggly over a hot parking lot. Light passing through layers of air at different temperature is bent..

Because of this refraction, the light coming from a single point (a distant star) comes to you by slightly differing paths second by second. The refraction is very small, but enough to cause the twinkling.

Even though stars and planets look very similar to the naked eye, a planet covers much more of the sky than a star does. For example, Jupiter covers about 30,000,000 times as much sky as the nearest star. Because of this, the light from Jupiter is not a point source but comes to us spread out over a small patch of sky. This causes the refractions (and twinkling) effects to be spread out as well. Light being refracted away from you from one part of the planet is smeared out by all the light still reaching you.

You can verify this a couple ways. If you have somewhere with a distant view of city lights, you will see that nearby lights (a couple miles away) do not twinkle while distant lights (10 miles or so) do twinkle. For comparison, the size of Jupiter in the sky is about the same as a street light that is 1 mile away. The nearby lights act like Jupiter, the distant ones are like the stars.

A second verification is that, through a telescope, stars do not twinkle. The telescope gathers light over a large enough area (compared to the pupil of your eye) that the twinkling effects are smeared out.

Answer 3

Twinkling occurs because of our atmosphere...it's not the stars doing it themselves. Because of the unsteadiness of air motion, the appearance of stars looks "twinkly" when filtered through it. The planets are MUCH closer to Earth and have a much larger "apparent diameter" than the further stars, which look like pinpoints even in our largest telescopes...as a result, the filtering affect from our atmosphere is not as prevalent...so you won't see planets twinkle.
You'll notice stars tend to twinkle more wildly in the winter....that's because the colder winter air is much more unsteady compared to the relatively steady summer air.

Answer 4

a superstar as sen from earth is a factor source, jointly as a planet has discernible volume. through atmospheric turbulence a factor source looks wavering or twinkling. In a source it rather is unfolded the twinkle is evened (averaged) out to make it seem stable.

Answer 5

To put it simply, star light is alternating and the planet is reflected light from a star.

Answer 6

Planets are VERY bright. If see a bunch of stars and you see something brigher than that, it is more than likely a planet.

Answer 7

stars produce light, planets do not

Answer 8

Stars are on fire. Planets aren't.

Answer 9

probablly because stars are huge gases,constantly exploding & planets are bodies of mass.

Answer 10

timespiral should get the ten, I believe that answer is right on