Earth Shadow & Twilight Arch, Stockholm - A 140° panorama by Peter RosÚn. ©Peter Rosén, shown with permission.

The dark wedge of the Earth's shadow rises to the left. The shadow is cast through the atmosphere and stretches 180░ around the horizon. It is topped by the pink glow of the 'anti-twilight arch', also called the 'Belt of Venus'. There the air is lit by scattered and deeply reddened sunlight on the shadow's edge. It mingles with the deep blues of the eastern sky to form the pink/purple hues.

To the right the western horizon is lined with a narrow band of reds and yellows, the 'twilight arch'. The westward atmosphere is still sunlit and near the horizon where the atmospheric path is thickest the sun's rays are reddened by Rayleigh scattering then further scattered to our eyes.

The twilight arch's brightness and colours change as the sun gets further below the horizon. The twilight hues and shades alter from minute to minute. We have seen many volcanic twilights recently - 'ordinary' ones have their moments too!

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