16-6-2023 (HONG KONG) On the evening of June 15th, an extraordinary sight unfolded in the skies above Chek Lap Kok Airport, leaving Hong Kong citizens perplexed and awestruck. Photographs taken by a local resident revealed the presence of two suns, one positioned above the other.
Renowned meteorologist and former assistant director of the Hong Kong Observatory, Leung Wing-mo, confirmed that this was neither a common “sun dog” occurrence nor a light pillar. In his extensive experience, he had never encountered such a phenomenon before and found himself bewildered by the mystery of the dual suns.
A netizen’s Facebook post proposed a possible explanation, suggesting that the unusual sighting could be attributed to the reflection of water vapor. The photographs showcased a hazy sky with two suns neatly stacked on top of each other.
Leung Wing-mo, however, dismissed the water vapor reflection theory, stating that the appearance of multiple suns in the sky typically falls into two categories: “sun dogs” or light pillars. Sun dogs arise when sunlight refracts through small ice crystals in the atmosphere, resulting in the illusion of two additional suns flanking the real sun. Light pillars, on the other hand, occur when light reflects off ice crystals, creating vertical columns of light.
Nevertheless, Leung Wing-mo emphasized that the double sun phenomenon witnessed at the airport differed from these known optical phenomena. At present, the cause behind this extraordinary event remains unknown.
In addition to the dual suns, the evening sky took on mesmerizing hues of pink and purple after a rainfall, accompanied by the appearance of a vibrant rainbow. Numerous individuals seized the opportunity to capture this stunning spectacle on camera.
A similar occurrence of two suns side by side in the Chinese sky gained significant attention in 2011. The footage showcased one blurry, orange sun juxtaposed with a clear, yellow sun, the former slightly elevated. The double sun phenomenon left many observers puzzled, questioning the nature of this celestial phenomenon.
Jim Kaler, an astronomer at the University of Illinois, explained that the double sun image is an outcome of optical refraction, though it remains a rarity that lacks a comprehensive scientific explanation. Mirages typically manifest when atmospheric particles refract, or bend, light. Typically observed near the horizon, where air density is higher, mirages usually appear vertically above or below the original light source—not beside it, as seen in the video. Kaler postulated that an unusually dense atmospheric layer may have passed in front of the sun, causing this captivating and unusual effect.
Recorded instances of horizontally-aligned double images of the sun and moon have been documented in the book “Light and Color in the Outdoors” by Flemish astronomer Marcel Minnaert. This comprehensive reference work presents numerous accounts of sun and mock suns being at the same altitude, attributing the phenomenon to abnormal refraction. Remarkably, the images of the sun and moon depicted in these reports appeared sharp and matched the size of their real counterparts.
Despite these historical records, experts in atmospheric optics consulted regarding the double sun effect showcased in the video remained perplexed. None of them had witnessed anything quite like it. Kaler suggested that the occurrence might be linked to an atmospheric anomaly, where a concentrated “blob of atmosphere” created a mirage-like effect. However, the precise cause of this extraordinary phenomenon continues to elude scientific understanding.
