On 20 October 2026, NASA's Astronomy Picture of the Day (APOD) featured a rainbow with a fan of light and dark bands spreading across it. The bands are anticrepuscular rays.
These rays form when clouds or terrain block parts of the low Sun's light, so long stripes of sunlight and shadow stretch across the sky. The stripes are actually parallel. Perspective makes them seem to spread out from the Sun, cross the sky above the observer and meet again at the antisolar point, which lies directly opposite the Sun.
A rainbow is always centred on that same antisolar point, so the rays look like spokes running towards the middle of the arc. Both effects come from simple geometry: sunlight, raindrops or haze, and the observer's line of sight. APOD posts one image like this each day, with a short explanation written by a professional astronomer.
