APOD
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
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 fibratus. 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 in 2021 near North Fork Mountain in West Virginia, USA.
Tomorrow's picture: open space
| Date: | August 2, 2026 |
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| Credit & Copyright: | Christa Harbig |
| Authors & editors: | Robert Nemiroff, Jerry Bonnell, Cecilia Chirenti, Keighley Rockcliffe |
| A service of: | ASD at NASA / GSFC, |
