Skywatchers in Chile were star-struck by this incredible lunar halo

Observers at the La Silla Observatory on the border of Chile’s Atacama Desert were studying the stars and constellations last week when they saw something spectacular: A bright lunar halo had formed in front of the Orion constellation and Sirius, the brightest star in our sky.

The technical term for a lunar or solar halo is a “circumscribed halo.” Similar to sun dogs, lunar and solar halos belong to the family of ice halos, which are optical phenomena formed by the refraction of sun on hexagonal ice crystals suspended high up in the atmosphere, most commonly in cirrus clouds. These are also known as 22-degree halos, because the ring of light forms 22 degrees from the sun.