APOD: 2026 August 2 – A Fire Rainbow over West Virginia

NASA’s Astronomy Picture of the Day (APOD) highlighted a striking atmospheric phenomenon known as a circumhorizon arc, often called a “fire rainbow” due to its vivid, flame-like appearance. The image, captured near North Fork Mountain in West Virginia in 2021, showcases a rare optical display formed by ice crystals in high-altitude cirrus clouds. The phenomenon occurs when sunlight refracts through horizontally aligned hexagonal ice crystals, creating a vivid spectrum of colors parallel to the horizon.

The circumhorizon arc requires specific conditions to form, including a Sun elevation of at least 58 degrees and the presence of cirrus fibratus clouds below it. These high, wispy clouds must contain flat, hexagonal ice crystals aligned in a uniform manner to collectively refract sunlight in the same direction. This alignment is uncommon, making the sighting of such arcs relatively rare compared to other atmospheric optical phenomena.

The APOD entry, curated by professional astronomers, provides a brief explanation of the science behind the image, emphasizing the role of ice crystal orientation and sunlight refraction. The photograph serves as a visual example of how atmospheric conditions can produce visually stunning and scientifically intriguing displays. APOD has been sharing daily images of the cosmos since its inception, offering educational insights into celestial and terrestrial phenomena.

Tomorrow’s APOD is expected to feature a different astronomical or atmospheric event, continuing the tradition of showcasing captivating imagery with accompanying scientific context. The series remains a popular resource for astronomy enthusiasts and educators, providing accessible explanations of complex natural phenomena.