I live in the Netherlands and recently I have been seeing an orange glow in the sky at night, in the northwestern direction. What is the cause of this? And why is it in the northwestern direction (I have seen it a couple of times recently, all in the same general direction).
[Physics] the cause of orange sky glow
atmospheric scienceeveryday-lifeoptics
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The sky does not skip over the green range of frequencies. The sky is green. Remove the scattered light from the Sun and the Moon and even the starlight, if you so wish, and you'll be left with something called airglow (check out the link, it's awesome, great pics, and nice explanation).
Because the link does such a good job explaining airglow, I'll skip the nitty gritty.
So you might be thinking, "Jim, you half-insane ceiling fan, everybody knows that the night sky is black!" Well, you're only half right. The night sky isn't black. The link above explains the science of it, but if that's not good enough, try to remember back to a time when you might have been out in the countryside. No bright city lights, just the night sky and trees. Now when you look at the horizon, can you see the trees? Yes, they're black silhouettes against the night sky. But how could you see black against black? The night sky isn't black. It's green thanks to airglow (or, if you're near a city, orange thanks to light pollution).
Stop, it's picture time. Here's an above the atmosphere view of the night sky from Wikipedia:
And one from the link I posted, just in case you didn't check it out:
See, don't be worried about green. The sky gets around to being green all the time.
I'm not a professor of chemistry or anything, but on a computer screen, Orange equals about 2 parts red and 1 part green on the RGB scale.
Using the chart in the link below:
http://www.scienceclarified.com/Ga-He/Gases-Properties-of.html
You can get green from Chlorine gas and Red/Brown from NO2. Chlorine is highly reactive so in reality, I don't think it would stay in an atmosphere, but for a simulation, . . . why not.
A mix of Redish Brown and Green lit by a bright sun would equal an Orange like color.
It's worth noting that the sky isn't colored gas but only a tiny refraction effect that's spreads the blue light around the sky. It's noticable cause the atmosphere is miles thick. A colored gas and you'd only need trace amounts of it with an atmosphere a few miles thick and it would have a filtering maybe clouding effect so you wouldn't see the stars very well at night.
I couldn't find any data on which gases refract Orange light more than other colors, but that would work too. A thicker atmosphere might also work where the blue light doesn't make it all the way through that much atmosphere (like what happens at sunset when the sky/atmosphere turn Orange/Red).
Another way to do it would be orange dust, orange clouds or maybe an Orange star (there are many Orange stars) and less refraction - but the science of exactly how coloring of an atmosphere works is kinda complicated. I'm not smart enough to give you a complete answer.
Best Answer
What kind of Orange and how much of the sky did it fill?
Low pressure sodium lights are common in lighting cities and highways. Is there a big city/freeway northwest of you? I suppose under the right conditions you could see sky glow from a large city a long way away.
If you are at a very dark clear site (unlikley in the Netherlands) it could be zodiacal light - sunlight reflecting off the dust that fills the solar system. Although I don't know you could see it with the naked eye at a regular site