dualsunset

A dual sunset is a rare atmospheric phenomenon where an observer sees two distinct suns setting. This illusion is typically caused by atmospheric refraction, specifically a phenomenon known as a mirage. The most common type of mirage that can create a dual sunset is a superior mirage, which occurs when light rays bend as they pass through layers of air with different densities, usually due to temperature inversions near the Earth's surface.

In the case of a dual sunset, a layer of cold, dense air near the surface, topped by a layer of warmer, less dense air, can refract the light from the setting sun. This bending of light can create a virtual image of the sun that appears above or below the actual sun, or even to its side. The observer perceives both the real sun and its refracted image, leading to the impression of two suns setting.

Dual sunsets are most frequently observed over bodies of water like oceans or large lakes, or over flat, open terrain where temperature inversions are more likely to form. The effect is transient and depends on precise atmospheric conditions. As the sun sinks lower and the temperature gradients change, the mirage effect diminishes, and the two images merge back into one or disappear. While visually striking, it is an optical illusion and does not involve two actual celestial bodies.