What is the Light Around the Moon Called?

Have you ever looked up at the night sky and noticed a faint glowing ring around the moon? This spectacular phenomenon, also known as a lunar halo, has captivated sky-watchers for centuries. But what exactly is the light around the moon called, and what causes it to occur? In this blog post, we will explore the fascinating world of lunar halos and delve into the science behind this ethereal spectacle.

The Basics of Lunar Halos

A lunar halo is a ring of light that surrounds the moon in the night sky. It appears as a luminous circle, often spanning around 22 degrees in radius, although larger halos have been observed under certain atmospheric conditions.

Typically, the halo is pale white or gray in color, but occasionally it can display hints of red or other colors due to the scattering of light. The intensity of the halo may vary, with some halos appearing more pronounced and detailed than others.

Understanding the Optical Phenomenon

So, what causes this striking display of light around the moon? The answer lies in the interaction of the moonlight with ice crystals in the Earth’s atmosphere.

When the moonlight encounters these tiny ice crystals, which can be found at high altitudes in cirrus clouds or even in the atmosphere near the ground, it undergoes refraction. Refraction is a phenomenon where light bends as it passes through different mediums, such as air or water.

As the moonlight enters the hexagonal ice crystals, it gets refracted, bending at a specific angle. The angle of refraction depends on the size and orientation of the ice crystals, leading to the dispersion of light into a halo shape. This dispersion is responsible for the creation of a circular ring around the moon.

In addition to refraction, another phenomenon known as internal reflection also plays a role in the formation of lunar halos. Internal reflection occurs when light rays bounce inside the ice crystals before leaving. This bouncing effect enhances the visibility of the halo and contributes to its aesthetic appeal.

The Shape and Size of Lunar Halos

Lunar halos are not always perfectly circular. Their shape can vary depending on the position of the observer and the properties of the ice crystals involved. In some cases, the halo may appear more elliptical or even possess more elaborate arcs and spots.

The size of the lunar halo is determined by the angle of refraction and the size distribution of the ice crystals. As mentioned earlier, a typical halo spans an angle of approximately 22 degrees from the center of the moon. However, the diameter of the circle can increase or decrease based on atmospheric conditions.

Under specific circumstances, larger halos, known as “moon rings” or “winter rings,” can be observed. These halos extend beyond the 22-degree radius and are often more vibrant and visually striking.

Other Atmospheric Optics Similar to Lunar Halos

While lunar halos are one of the most well-known atmospheric optic phenomena, they are not the only ones. Here are a few other similar phenomena that can occur on Earth:

• Sun Halos: Similar to lunar halos, these are circular rings of light that appear around the sun during the day. They are caused by the same refraction and scattering processes, but are less frequently observed due to the bright sunlight.
• Coronas: Coronas are colorful rings that form around the sun or the moon. Unlike halos, they result from diffraction, which is the bending of light when it passes around small obstacles, like cloud droplets or water vapor.
• Parhelia or Sun Dogs: These are bright spots of light that occasionally appear on both sides of the sun. They are caused by the refraction of sunlight through ice crystals, similar to lunar halos.

Cultural Significance and Folklore

Lunar halos have often been regarded as mystical and enchanting, leading to various cultural interpretations and folklore.

Throughout history, different cultures have attached different meanings to the appearance of lunar halos. Some have considered them as omens of impending bad weather or upcoming celestial events. In certain societies, lunar halos have been associated with luck, fortune, or even supernatural encounters.

Modern science has unravelled the scientific explanation behind lunar halos, but the allure and fascination they evoke are still deeply rooted in cultural beliefs and imaginations.

Conclusion

As we gaze up at the moon and marvel at the luminous ring that surrounds it, it’s awe-inspiring to realize the complex scientific principles at play. The interaction between moonlight and ice crystals in the atmosphere creates a mystical display known as a lunar halo. These ethereal rings of light have captivated human imagination for centuries and continue to enchant us to this day.

So, the next time you find yourself beneath a celestial dome aglow with moonlight, take a moment to appreciate the beauty of the lunar halo and the wonders of the natural world. It is a reminder of the grandeur and mystery that lies beyond our atmosphere and the magic that can be found in even the simplest of optical phenomena.