A sun halo spotted in Bukit Panjang at 1.46pm on March 15. The Straits Times/Asia News Network
SINGAPORE — If you happened to lift your gaze to the skies around midday on March 15 in Singapore, you may have spotted a bright ring of light around the sun.
Known as a sun halo, photos of the rare sighting quickly made their way across social media and messaging platforms after it was spotted at around 11am.
These photos were taken by people at locations across the island, from Chinese Garden to Woodlands, Serangoon Gardens and Bedok, between 11am and around 3pm.
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They included Senior Minister Lee Hsien Loong, who took to Facebook to share a photo of the optical phenomenon at about 2.40pm.
“A rare and spectacular sight in the skies above! I am told that this phenomenon is known as a 22-degree halo or a sun halo,” said SM Lee.
A sun halo forms when sunlight interacts with ice crystals in the atmosphere. These crystals are from thin clouds so high in the sky that they are made of ice rather than water droplets.
However, a 22-degree halo specifically refers to the ring of light having a radius of about 22 degrees, said Professor Matthias Roth, who teaches geography at the National University of Singapore.
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“As light enters one face of the ice crystals and exits through another, it is bent by about 22 degrees, which accounts for the radius of the halo,” he said.
According to the National Environment Agency, this is not a common sight in Singapore as sun halos tend to be covered by low to mid-level clouds.
The agency previously said that it is difficult to forecast the precise location of these ice crystals in the atmosphere, which will determine where the halo can be sighted.
While it is safe to look at the halo itself with the naked eye, the agency added that it will be dangerous to look at the sun directly without proper protection.
A sun halo was also previously spotted in Singapore on Sept 22, 2020.