Explanation: What is creating the colorful pattern in this cloud? High above the ground, ice crystals in a distant cirrus cloud act like tiny floating prisms. This atmospheric optical phenomenon is known informally as a fire rainbow because of its flame-like colors, but its scientific name is a circumhorizon arc or circumhorizontal arc. It typically appears as a bright, colorful band running parallel to the horizon. For a circumhorizon arc to form, the Sun must be at least 58 degrees above the horizon, and the sky must contain suitable cirrus clouds—in this case, cirrus fibratus. The cloud must also contain numerous, flat, hexagonal ice crystals that are aligned horizontally. When sunlight passes through these crystals, it is refracted in a similar direction, producing the vivid colors of the fire rainbow. Because the required solar angle and crystal alignment are relatively uncommon, circumhorizon arcs are unusual atmospheric phenomena to observe. This featured fire rainbow was photographed in 2021 near North Fork Mountain in West Virginia, USA.
Tomorrow’s picture: meteoric photobomb
Source: science.nasa.gov