Lunar corona

Last updated on September 16, 2023

Lunar Corona: A Spectacular Atmospheric Phenomenon

Have you ever looked up at the night sky and noticed a beautiful ring of colors surrounding the moon? This captivating optical phenomenon is known as a lunar corona. It occurs when light from the moon interacts with tiny particles or droplets in the Earth's atmosphere, creating a stunning display of colors. While the existing content provides a brief overview of lunar coronae, let's dive deeper into this fascinating atmospheric optics topic and explore some additional details.

How is a Lunar Corona Formed?

Lunar coronae are formed by the diffraction and interference of light waves as they pass through the atmosphere. When moonlight encounters small particles or droplets, such as those found in clouds or mist, it scatters in different directions. The scattered light waves then interact with each other, creating a series of bright and colorful rings around the moon.

The Role of Ice Crystals and Water Droplets

While the existing content mentions that coronae are formed by ice crystals, it's important to note that supercooled water droplets can also contribute to their formation. In extremely cold temperatures, water droplets can remain in a liquid state even when the temperature is below freezing. These supercooled water droplets, along with ice crystals, act as the scattering agents that produce the lunar corona.

Factors Affecting the Appearance of a Lunar Corona

The appearance of a lunar corona can vary depending on several factors, including the size and shape of the particles or droplets in the atmosphere. For a corona to exhibit exceptional finesse, as mentioned in the existing content, the scattering agents must be very uniform in size and distribution. This uniformity allows for precise diffraction and interference of light waves, resulting in well-defined rings around the moon.

Additionally, the visibility of a lunar corona can be influenced by weather conditions. The presence of fine dust or aerosols in the atmosphere can enhance the scattering of light and intensify the colors of the corona. Windy conditions, as mentioned in the existing content, can also play a role in creating a more distinct corona by causing the particles or droplets to move and interact with the moonlight in unique ways.

The Appearance of Multiple Rings

In some cases, like the lunar corona imaged by Lauri Kangas in 2004, multiple rings can be observed surrounding the central aureole. These additional rings are caused by multiple scattering events within the atmosphere. As the moonlight interacts with different layers of particles or droplets, each layer contributes to the formation of a separate ring, resulting in a mesmerizing display of concentric circles around the moon.

Similarities to Solar Coronae

Lunar coronae share similarities with their solar counterparts, known as solar coronae or solar halos. Both phenomena are formed by the diffraction and interference of light waves as they interact with particles or droplets in the atmosphere. However, there are some distinct differences between the two. Solar coronae are typically larger and more vivid due to the intense brightness of the Sun compared to the moon. Additionally, solar coronae often exhibit a wider range of colors, including reds, greens, and blues, while lunar coronae tend to display softer hues.

Capturing the Beauty of Lunar Coronae

Photographing lunar coronae can be a challenging yet rewarding endeavor. Due to the brightness of the moon, overexposure is often necessary to capture the delicate rings surrounding it. This can result in the moon itself appearing as a bright white disk or being completely washed out. However, by adjusting exposure settings and using specialized techniques, photographers can capture the intricate details and vibrant colors of lunar coronae.

Cultural Significance

Throughout history, lunar coronae have captivated human imagination and inspired various cultural interpretations. In some folklore and mythology, lunar coronae have been associated with omens, supernatural events, or even messages from celestial beings. Their ethereal beauty has also been a source of inspiration for poets, artists, and writers, who have sought to capture their enchanting qualities in their works.

The Joy of Observing Lunar Coronae

Observing a lunar corona can be a truly magical experience. The sight of the moon surrounded by a delicate ring of colors can evoke a sense of wonder and awe. Whether you witness it while stargazing in a serene countryside or from the comfort of your own backyard, take a moment to appreciate the intricate dance of light and particles that creates this mesmerizing spectacle in the night sky.

Conclusion

Lunar coronae are a captivating atmospheric optics phenomenon that adds a touch of magic to our nights. Formed by the diffraction and interference of moonlight with particles or droplets in the atmosphere, these beautiful rings of colors offer a glimpse into the complex interactions between light and matter. Whether you're an avid sky watcher or simply appreciate the beauty of nature, keep an eye out for lunar coronae and let their ethereal presence fill you with a sense of wonder and awe.

Three rings surround the central aureole of this lunar corona imaged by Lauri Kangas (site) on 31st January 2004. The three quarter moon is not visible because of the necessary overexposure needed to capture the coronal rings. "Tonight, while I was shoveling snow I noticed a really distinct corona around the moon. The temperature was -8C and the wind was really cold and blowing fine dusty snow around. I think coronae are usually caused by water droplets but it was way too cold for liquid water, at least at ground level!" Coronae are formed by ice crystals, supercooled water droplets might also have been present. Whatever created it, a corona of this exceptional finesse required very uniform droplets or particles. Image ©2004 Lauri Kangas.

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Reference Atmospheric Optics

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