Where does the Moon get its halo from? 

Just like the sun, the moon too has a ring surrounding it, that is often regarded as the lunar halo. It is a circular band of coloured light that is caused by alternate reflection and refraction of light by ice crystals in the atmosphere. 

Even though the moon’s halo is always there around it, we get to experience it occasionally. Lunar halo is so rarely visible that kids for generations believed that it is a magical occurrence and only few people get to witness it in their lifetime. Lunar halo is nothing but a unique, amazing and once in a blue moon natural occurrence. Keeping this in mind, let us explore the science behind this natural phenomenon.  

How is the lunar halo formed? 
Lunar halo, also called 22° halo is a phenomenon formed when the moonlight (which is in fact sunlight reflecting from the moon) is refracted from ice crystals floating in the upper atmosphere in between 5 and 10 kilometres. These ice crystals are usually formed out of high-altitude clouds called the cirrus clouds that have millions of ice crystals within them. The ice crystals refract the lunar light at an angle of 22 degrees, resulting in a beautiful halo around the moon.  

How is the lunar halo visible to humans on earth? 
The lunar halo is only visible to humans on earth when the millions of ice crystals are aligned in such a way that they help refract the moonlight towards naked human eyes. However, how this kind of alignment occurs is still a mystery to scientists. In fact, every time this rare event happens, space scientists try and analyse the reason behind the alignment.  

However, the most fascinating story perhaps is that, each human gets to see and experience their unique and personal halo. This happens because the moonlight refracted from the ice crystals gets aligned according to a person’s position on ground. This means, that every slight movement from a specific position will offer a distinct view of the lunar halo.  

Ring around the Moon, signals rain: Is there a scientific base behind this folklore? 
The folklore “Ring around the Moon, signals rain” is neither true nor false. The real reason behind linking lunar halos to rainy weather is the cirrus clouds. These clouds that are indirectly responsible for formation of the halos, precede rain clouds on several occasions. In fact, a lunar halo is often spotted right after a downpour, almost like a rainbow.