A Stream of Anticrepuscular Rays

On top of observing astronomical events in the northern skies, Gemini North — one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab— is also set in an environment of gorgeous sunsets near the summit of Maunakea, Hawai‘i. Every so often, though, Gemini North is the site of something special. Upon closer inspection, a stream of shadow can be seen streaking across the right side of the image, outlined by parallel beams of light known as anticrepuscular rays. These rays are caused by clouds obscuring the dim, backscattered sunlight and appear to converge on a point directly opposite the Sun, known as the antisolar point. If these rays originated directly from the Sun, they would be called crepuscular rays. Anticrepuscular rays require the right environment to be created so they are difficult to glimpse.