Why Don't Planets Twinkle?

[nebulosity. (Jo)]

Can anyone tell me??? It's doing my head in

The more I think about it the stranger in seams.

Jo

[doppler (Rick)]

I think it is beause planets shine by reflected light from the sun and are not very bright whereas stars generate their own light and are exteamly bright but are so far away that they are a point of light. The variations in the earths atmosphere makes them appear to twinkle.

Rick

[astroron (Ron)]

Originally Posted by nebulosity.

Can anyone tell me??? It's doing my head in

The more I think about it the stranger in seams.

Jo

Simple answer here.

http://earthsky.org/space/why-dont-p...le-as-stars-do
Cheers

[LewisM]

Simply because of how close the planets are to Earth in relation to the distances to stars. A star will seem small even in a telescope, so the light from a star upon entering an atmosphere will be more easily disturbed thanks to the small "size and breadth" of the light. The light from the planets, on the other hand, is "larger/wider" for want of a better term, so the light, not being a pinpoint per se like a star's light, while it still "twinkles" tends to neutralise the apparent light shift simply due to the size of the the reflected light (ya know, this is kinda hard to explain!)

Have a look also how much A-centauri twinkles in comparison to say Sirius. You'll notice a BIG difference.

Aw stuff it, google it

[LewisM]

Yeah, what Andrew said and I tried to say

[mithrandir (Andrew)]

Originally Posted by LewisM

Yeah, what Andrew said and I tried to say

Lewis, I deleted my post because it pretty much duplicated yours. Let me try to remember what I said.

Stars are so far away that they appear as pinpoints of light. Any disturbance in the atmosphere causes the light path to change so the star appears to move, which you see as twinkling.

Planets are close enough that they appear as a disk. The atmospheric disturbance affects the light from the planet the same as it does stars but because the disturbance is less than the size of the disk you don't see any twinkling.

Taking photos of planets has to make allowance for the atmospheric effects. You do this by taking hundreds or thousands of images (normally using a video style camera) and only keeping the best few percent of them to combine.

[nebulosity. (Jo)]

Thanks for your comments guys I think I've got it

The twinkle of the planets is hidden behind the disk

Thanks again, I think I can go rest my head now.

Jo

[TrevorW]

Stars twinkle, planets don’t.

Okay, that’s not actually correct. The stars, planets, even the Sun and Moon twinkle, all in varying amounts. Anything outside the atmosphere is going to twinkle.

If you’re feeling a little silly using the word twinkle over and over again, we can also use the scientific term: astronomical scintillation.

You can’t feel it, but you’re carrying the entire weight of the atmosphere on your shoulders. Every single square inch of your skin is getting pushed by 15 pounds of pressure. And even though astronomers need our atmosphere to survive, it still drives them crazy. As it makes objects in space so much harder to see.

Stars twinkle, I mean scintillate, because as light passes down through a volume of air, turbulence in the Earth’s atmosphere refracts light differently from moment to moment. From our perspective, the light from a star will appear in one location, then milliseconds later, it’ll be distorted to a different spot.

We see this as twinkling.

So why do stars appear to twinkle, while planets don’t?
Stars appear as a single point in the sky, because of the great distance between us and them. This single point can be highly affected by atmospheric turbulence. Planets, being much closer, appear as disks.

Read more: http://www.universetoday.com/25345/w...#ixzz2pI4AxQQS