May 19, 2019
The oldest light in the universe still hums faintly through space, a relic of the beginning itself.
A Circumhorizontal Arc Over Ohio
Birthday · May 19, 2019
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APOD published May 19, 2019. Credit: Todd Sladoje. A publication-date match, not a photo taken on your date. Independent of NASA.
Why would clouds appear to be different colors? The reason here is that ice crystals in distant cirrus clouds are acting like little floating prisms. Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc lies parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present. Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner. Therefore, circumhorizontal arcs are quite unusual to see. This circumhorizon display was photographed through a polarized lens above Dublin, Ohio in 2009.
Image credit: Todd Sladoje