WILT #12: Why do some stars flicker?

WILT #12: Why do some stars flicker?

This shouldn’t have been a difficult one but it’s something I’ve been meaning to look up, and now, instead of saying “hmm, I’ll have to look that up later”, I actually try and do it now.

We’re in a lot of rural areas all year long, with amazing stars due to dark night skies, so I’ve been meaning to learn more about astronomy, I bought a book, that I’ve yet to delve into much, but I wondered again today simply why stars flicker. Maybe a parent explained this to you, or you had a helpful physics teacher,  (Chemistry for the win!) but I have to look these things up.

The scientific name for the twinkling of stars is stellar scintillation (or astronomical scintillation). Stars twinkle when we see them from the Earth’s surface because we are viewing them through thick layers of turbulent (moving) air in the Earth’s atmosphere. Stars (except for the Sun) appear as tiny dots in the sky; as their light travels through the many layers of the Earth’s atmosphere, the light of the star is bent (refracted) many times and in random directions (light is bent when it hits a change in density – like a pocket of cold air or hot air). This random refraction results in the star winking out (it looks as though the star moves a bit, and our eye interprets this as twinkling). Stars closer to the horizon appear to twinkle more than stars that are overhead – this is because the light of stars near the horizon has to travel through more air than the light of stars overhead and so is subject to more refraction. Also, planets do not usually twinkle, because they are so close to us; they appear big enough that the twinkling is not noticeable (except when the air is extremely turbulent). Stars would not appear to twinkle if we viewed them from outer space (or from a planet/moon that didn’t have an atmosphere). (source)Twinkle

I suppose, for some reason, that atmosphere never crossed my mind at all, even though it seems fairly obvious now. I thought it had more to do with my eyes trying to translate colorful light-waves and they couldn’t quite render the colors to my brain, or that it was more of an optical illusion. Which in a way it sort of is, but it has a culprit.

 

So now, I really want to know what stars look like from the International Space Station. This is crazy!

You can see that many of them still appear to have color, however they aren’t tinkling or changing color as they would from earth. Their color depends on their temperature, and we’re still not able to see all the colors without a prism (like green).

Here’s a summary of the dominant color and temperatures of the main classes of stars, along with examples of stars that belong to each class:

starcolors
– See more at: http://oneminuteastronomer.com/708/star-colors-explained/#sthash.ei4RgYs2.dpuf

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