28 October 2007
Mock Sun over the Bibliotheca Alexandrina
A colorful mock sun (arrowed) shines in high altitude, wispy clouds to the west of the Sun. The Sun, encircled by a reddish hue, is to the left of image. Mock suns form due to the passage of sunlight through two types of high clouds, known as cirrus clouds and cirrostratus clouds.
Photo by Aymen Ibrahem, Senior Astronomy Specialist
On the morning of 28 October 2007, there were patterns of high clouds over Alexandria, Egypt. BA Senior Astronomy Specialist Aymen Ibrahem captured interesting images of these clouds and a fascinating optical atmospheric phenomenon, known as mock sun that gleamed over the Bibliotheca Alexandrina.
High clouds are composed of small ice crystals. They often form at altitudes of at least 6,000 m. The major types of high clouds are termed cirrus, cirrostratus and cirrocumulus, respectively. These clouds are often wispy and transparent.
Mock suns, also known as sundogs, mostly form due to the refraction of sunlight by the ice crystals in cirrus or cirrostratus clouds. They resemble a smaller, fainter Sun, located nearby the Sun. There may be two mock suns, located on either side of the Sun. The observer may have the impression of viewing three Suns in the sky. Some ancient texts actually described mock suns as double suns. Mock suns are usually located at 22° from the Sun.
"At about 8:24 am, while I was observing drifting high clouds and aircraft contrails, my eyes caught a bright, beautiful mock sun glowing in the clouds, to the west of the Sun," said Ibrahem. "It resembled a small pale patch of a rainbow, and lasted about 5 minutes."
At 8:33 am, Ibrahem recorded another mock sun. It was considerably fainter than the first mock sun. At 8:57, Ibrahem imaged another bright mock sun, visible to the east of the Sun. Some of his images are presented in the picture gallery below.
Picture Gallery
Fig (1)
A Colorful Mock Sun and Aircraft Contrails
The image shows a bright, colorful mock sun and aircraft contrails over the Bibliotheca Alexandrina.
Photo by Aymen Ibrahem, Senior Astronomy Specialist
Fig (2)
A Faint Mock Sun
Photo by Aymen Ibrahem, Senior Astronomy Specialist
Fig (3)
A Close-up of a Colorful Mock Sun (arrowed)
Photo by Aymen Ibrahem, Senior Astronomy Specialist
Further Reading
A Cloud and Its Shadow
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A Spectacular Sunset Wows Sky Observer
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Golden Sunset over Alexandria
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Aymen Mohamed Ibrahem
Senior Astronomy Specialist