Anticrepuscular rays are an optical phenomenon where sunlight passes through gaps in clouds near the setting Sun, creating an unusual rainbow effect that appears to converge in front of the observer.

An Anticrepuscular Rainbow Fan Image Credit: Aurelia Degli Esposti Explanation: This is an unusual rainbow. For one thing, the rainbow is not complete, appearing only in a sunlit fan -- but that by itself is not very unusual. What is most unusual is the fake location of the Sun. The Sun appears to be toward the front, just below those hills -- but it is not. That is not how rainbows work. Rainbows involve a backward reflection from falling rain, so that the Sun must really be behind you. In this case, gaps between clouds near the setting Sun allowed rays to cross the entire sky and appear to converge in front, an unusual phenomenon called anticrepuscular rays. The photo was taken with a phone last week at sunset in Presenzano, Italy. The seemingly reverse rainbow was noticed when hanging up laundry. https://science.nasa.gov/image-article/apod-2026-october-20-an-anticrepuscular-rainbow-fan/ #apod

October 20, 2026 An Anticrepuscular Rainbow Fan * Credit & Copyright: Aurelia Degli Esposti Explanation: This is an unusual rainbow. For one thing, the rainbow is not complete, appearing only in a sunlit fan -- but that by itself is not very unusual. What is most unusual is the fake location of the Sun. The Sun appears to be toward the front, just below those hills -- but it is not. That is not how rainbows work. Rainbows involve a backward reflection from falling rain, so that the Sun must really be behind you. In this case, gaps between clouds near the setting Sun allowed rays to cross the entire sky and appear to converge in front, an unusual phenomenon called anticrepuscular rays. The photo was taken with a phone last week at sunset in Presenzano, Italy. The seemingly reverse rainbow was noticed when hanging up laundry. https://science.nasa.gov/image-article/apod-2026-october-20-an-anticrepuscular-rainbow-fan/ #space #earth #rainbow #anticrepuscular #sun #astrophotography #photography #NASA #science #physics #nature #apod