What Causes A Ring Around The Moon?

What Causes A Ring Around The Moon heading

We often look at the full moon at night and notice a hazy looking ring (or halo) around it. It looks striking, especially when the conditions are just right. We often see the same phenomenon around the sun during daytime. 

Although there are a lot of theories and folklore surrounding this "supernatural" occurrence, very few people really know what exactly these rings (or halos) are or how they are formed.  

In this article, we take a look at what these ring are and how and how they are created. We also address a few common assumptions and look at some folklore surrounding these mystical objects in the sky.

ring around moon

Rings around the moon are nothing more than the refraction & reflection of the moonlight by millions of ice crystals present in cirrus clouds drifting at a heights of 20 000 feet (6000 meters) or more above the earth's surface. Depending on where you stand, the ice crystals needs to refract the light from the moon just at the right angle in order to see it. (This is why the circle is not visible to everyone. It all depends on your personal location.)

The rings (or halos) you see around the sun are in fact exactly the same phenomenon. Instead of moonlight though, it is sunlight that get's refracted and reflected in this case. 

What Causes The Rings Around The Moon

As mentioned in the previous section, the rings you see around the moon, is the result of the ice crystals in thin cirrus clouds refracting and reflecting the light in such a way that you can see a ring appearing from your unique location on the planet's surface. 

A few things need to be in place in order for you to clearly see these rings completely surrounding the moon though.

Obviously a full moon is ideal for the best viewing conditions. Secondly, a clear sky with only a thing layer of cirrus clouds high up in the atmosphere is essential. (The presence of thicker clouds lower down in the atmosphere will obscure or eliminate the effect.)

As the light from the moon (or sun) hits the cirrus cloud, it get refracted and "bend" by the ice crystals. The refraction by the ice crystals causes the light to be projected somewhere else. 

If the light is refracted or "bend" at a certain angle, specifically 22 degrees, the rings will become visible to the observer. (This also means the rings have a radius of about 22 degrees around the moon or sun.) That is why this occurrence is also referred to as 22-degree halos by scientists and meteorologists. 

Characteristics Of The Rings Around The Sun

On of the first things you will notice, is that the ring surrounding the moon do not have a clear and well-defined, but a rather fuzzy border. This partly due to the fact that so many millions of ice crystals are refracting the light in so many directions, that it is almost impossible to create a clear and well-defined border.

Although the ring around the moon has a  mostly hazy white color, other colors can also be observed. This a direct result of the faceted shape of the ice crystals.

22 degree halo

Very much like the shape of raindrops causing the different colors in a rainbow to appear, the faceted (specifically six sided) shape of ice crystals not only refract the light of the moon, but also breaks it up into its individual colors.

This is why you will occasionally notice some rings around the moon or sun to have a red tint on the inside and a blue tint on the outside. Since the moon isn't as bright as the sun, the rings around the moon mostly appear white, while the rings around the much brighter sun more often display these rainbow colors.

Another interesting fact about the rings surrounding the moon, is that the sky directly surrounding the ring/halo always appear darker than the rest of the night sky.

Finally, if you are lucky, you may catch a very rare glimpse of not one, but a double halo surrounding the moon or sun. 

Folklore And Superstitions Regarding Rings Around The Moon

For centuries now and among many cultures around the world, a ring around the moon was a clear sign that rainy weather is on the way.

And to be honest, this is neither a myth or a superstition. The presence of high cirrus clouds is very often an indication of wet and stormy weather on the way.

Cirrus clouds normally precedes low-pressure systems by a day or two, and as many of you may already know, low-pressure systems are normally at the heart of stormy wet weather. (You can read more about low-pressure systems and cold fronts in this article.)

The most noteworthy part about specific beliefs and folklore concerning rings around the moon, is the surprisingly lack of any specific ones.

Normally when it comes to the sun and moon, different cultures and religions look to these celestial bodies and attach some kind of significant meaning to changes in their appearances.

Significant events like the Full Moon, New Moon, and especially rare events like Solar Eclipses (especially combined to cause a "Blood Moon"), all have significant meaning and are often times of religious ceremonies, and even sacrifice for some pagan religions.

Sun Worshipping

The worshiping of the sun (and events surrounding the sun) is probably the oldest religion in the world and predates any recorded history. The worshiping of the sun gods Amun and Ra is well documented in ancient Egyptian history. 

Celebrations of the winter solstice, symbolizing the victory of light over darkness, also predates any Christmas celebrations during the same period, celebrating the birth of Christ.

Yet, despite all these celebrations and importance given to various events surrounding the sun and moon by various religions and cultures over the centuries, there is no evidence (not even a mention in any literature or the scriptures) of any attention given to the rings/halos surrounding the moon or sun.

The biggest irony, is that the only folklore surrounding the rings around the moon, is based on actual science. And that is the belief that the hazy ring we see at night surrounding the weather symbolize rainy weather. As it turns out, this belief is actually scientifically correct.

Conclusion

As you can clearly see, the visible ring/aura around the moon that sometimes occur under ideal conditions, is not nearly as mystical as one might think.

There is a very simple scientific explanation for it, which has everything to do with what is going on in our atmosphere, and nothing to do with what is happening in space around the moon itself.

You also learned that the multicolored ring we sometimes see around the sun, is actually exactly the phenomenon that occurs around the moon.

Feel free to leave me any comments, questions or suggestions, and I will get back to you as soon as possible.

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Until next time, keep your eye on the weather!

Wessel


Wessel Wessels
 

Lifelong weather enthusiast. Interest in all things weather-related, and how global climate and local weather interact. Home weather station owner for almost 2 decades, but still learning and expanding my knowledge every day. Keen on sharing my knowledge and get more people involved and interest in both their local weather and how it interacts with climate on a global scale. Love sharing my knowledge on home weather stations, how they work and the many ways you can use them to your advantage. All in all, just a bit of weather nerd.

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