Thanks to Mary Jane F.
Image Credit: Christa Harbig
Explanation: What’s happening to this cloud? Ice crystals in a distant cirrus cloud are acting like little floating prisms. Known informally as a fire rainbow for its flame-like appearance, a circumhorizon arc appears 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 present below — in this case cirrus fibrates. 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 somewhat unusual to see. The featured fire rainbow was photographed earlier this month near North Fork Mountain in West Virginia, USA.
The NASA site provides a photo daily that speaks of the ‘wonder’ in and beyond our immediate experiences. The site says “Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.”
It can be subscribed to daily, here: https://apod.nasa.gov/apod/