Lake Louise in Banff National Park

 Along Lake Louise in Banff National Park, Alberta, the sunset slowed the day to a standstill.

As the Sun dipped behind the mountains, a clean arc of color rose above it...perfectly curved, evenly spaced, and bright enough to mirror itself across the lake. The water stayed calm.

It was sunlight interacting with fine moisture and ice crystals in the air at the exact moment the Sun reached a low angle. The halo-like arc formed as light refracted and reflected, while thin clouds shaped the glow into a smooth, continuous band. The starburst came from the Sun’s rays slipping through gaps in the clouds, fanning outward before the light faded.

Everything had to align:
Sun angle, cloud height, air clarity, and still water. Shift any one of them, and the arc dissolves.
Within minutes, the colors softened, the arc thinned, and night reclaimed the sky.