An atmospheric optics event was recorded in Presenzano, Italy, on October 20, 2026, when a photographer captured an incomplete rainbow that appeared to fan forward from sunlit hills.

The image, taken at sunset with a mobile phone, shows a partial arc of colored light extending from the horizon toward the photographer. What makes the photograph unusual is the apparent position of the light source. The photographer initially believed the sun was positioned in front of the scene, just below the hills, but this contradicts standard rainbow formation physics.

Rainbows require sunlight to refract, reflect off water droplets, and exit at a 42-degree angle relative to the incoming light. This process creates a circular arc centered on the antisolar point, which lies directly opposite the sun from the observer's perspective. In this case, gaps between clouds near the actual setting sun allowed sunlight to scatter across the sky and converge in the direction of the photographer, creating the illusion of a forward-facing rainbow.

The phenomenon is known as anticrepuscular rays, which occur when sunlight passing through airborne droplets creates visible beams that appear to converge at the antisolar point. These rays are typically observed as dark columns extending away from the sun, but in this instance, the scattered light formed a visible arc.

Aurelia Degli Esposti, the photographer, documented the event while hanging laundry near Presenzano. The image was later featured by NASA's Astronomy Picture of the Day as an example of an uncommon atmospheric optical phenomenon.

The photograph demonstrates how variations in cloud cover and atmospheric conditions can create unexpected light patterns that challenge conventional understanding of rainbow formation. While the arc appears to extend forward, the underlying physics confirms that the light still originates from the sun behind the observer, consistent with established principles of optics.

This event contributes to the ongoing documentation of rare atmospheric phenomena, highlighting the value of public observation in advancing awareness of natural light behaviors.