Brilliant Halo at La Silla

A spectacular lunar halo — known as a 22° halo — formed in the sky above ESO’s La Silla Observatory. The optical phenomenon is a result of moonlight interacting with millions of ice crystals suspended in the atmosphere, forming a ring with an apparent radius of approximately 22° around the moon. It is also known as the “moon ring” or “winter halo”.

While this is a beautiful sight, it creates conditions which are not optimal for astronomical observations. Clouds and the bright light of the moon affect the quality and accuracy of astronomical observations. However, that does not diminish the allure of this ethereal sight, and in fact some stars remain visible. Notably, Sirius, the brightest star in the night sky, can be seen at the top edge of the image, just left of the centre.