We were in Solta, Croatia, when we looked up at the clear sky to see a start twinkling red-blue, like a disco light. I pulled out the Sky Guide app to see that this was Capella. I knew that stars appear to twinkle due to their light being refracted by our turbulent atmosphere before hitting the eye. But this particular star happened to be twinkling more than just about anything. We were wondering why.
It turns out that stars lower in the sky will twinkle more. Capella (which, TIL, is actually a star-system made of four stars!), starts low in the Northern evening sky. That way, the starlight has to travel more atmosphere before reaching us, which is responsible for the fabulous display of colors. Different wavelengths of light get bent in different angles by pockets of air with different densities, and as the atmospheric air moves around, we get to see different colors.
Capella eventually moves higher in the sky, and the disco effect is less pronounced just before dawn.
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