What is this, red, blue, white twinkling, star?

Question

I am from Germany and at 11 PM I was outside and I saw a star, rapidly twinkling in blue, red and white. At first, I thought it was a plane, but it didn't move.

I took a picture of it, but you can only see a blue-ish dot on the photo.

I am from Germany and the star was in a north-east direction and it's currently around 12 at night.

Here is a photo I took of the star:

This one is for the direction of the star. It's in the circle you can see there, all of the large stars in the photo are from an app-generated an overlay.

What about the other white dots (there are at least five that can't be stars)? Interfering street lights (reflections in the optics)? — Peter Mortensen, Mar 28 '22 at 19:42
What is your (approximate) location in Germany (the range in latitude is about 8° and 11° in longitude)? What is the field of view / (effective) focal length of the camera? — Peter Mortensen, Mar 28 '22 at 19:46

Greg Miller · Answer 1 · 2022-03-29T00:52:43.970

20

The star is most likely Vega.

It doesn't actually twinkle, the technical term for this is "scintillation", and is purely an atmospheric effect.

The general idea is that stars are so far away, they are infinitesimally small points of light. So, even the slightest changes in atmospheric temperature or pressure will cause the atmosphere to refract the light differently. And the different wavelengths of light are affected less (or more), causing the colors to separate out (similar to a prism).

You'll notice this tends to happen more to stars that are closer to the horizon. This is simply because you're looking through more atmosphere, and there's a largely likelihood of a significant change in refraction. And also because you'll be looking over close objects like roofs or pavement which are exchanging heat with the atmosphere.

It tends to happen with brighter stars mostly because your eye isn't sensitive enough to pick up the changes on dimmer stars. Planets are also less effected, because they are not nearly point sources like stars are.

edited Mar 29 '22 at 00:52

answered Mar 28 '22 at 01:37

Greg Miller

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+1 There are some actual images of colorful "twinkling" in this answer to Betelgeuse appears in a rainbow of colors through a Newtonian telescope See also What is "scintillation" and are "qualified pilots" aware of it? in Aviation SE. – uhoh Mar 28 '22 at 01:53
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"It doesn't actually twinkle, the technical term for this is "scintillation", and is purely an atmospheric effect." Isn't that what twinkling (in the context of stars) always is? This sentence seems to suggest that there might be some other, 'real' version of twinkling that we see stars doing. – dbmag9 Mar 28 '22 at 15:49
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@dbmag9 Yes, all star "twinkling" is actually scintillation. But there is a "real" (for lack of a better term) "twinkling" in the context of the English language that stars don't do. – HiddenWindshield Mar 28 '22 at 16:07
@HiddenWindshield stars "twinkle", they don't "flash". – James K Mar 28 '22 at 17:29
@JamesK I never said they did. – HiddenWindshield Mar 28 '22 at 20:20
I mean "flashing" is the "real twinkling", in the context of the English Language, that stars don't do. – James K Mar 28 '22 at 21:10
@DaveGremlin I think the edit you suggested is better added to the question rather than the answer. – Greg Miller Mar 29 '22 at 00:53
@GregMiller I made the edit because of this problem: https://astronomy.meta.stackexchange.com/questions/840/how-can-i-withdraw-a-down-vote – Dave Gremlin Mar 29 '22 at 00:57

What is this, red, blue, white twinkling, star?

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