Solar halo, rainbow catch fancy of skywatchers

KOLKATA: A halo that appeared around the sun around 10.45 on Wednesday morning and remained till noon had one and all gazing skyward and clicking photographs that were widely circulated. Later in the day, a rainbow appeared along the eastern edge of the city, leading to further delight among shutterbugs.


The celestial sight of the dazzling ring that formed a perfect circle around the sun enthralled viewers and had many wondering if it was a supernatural phenomenon. Astronomers though pointed out that the phenomenon, called the “22° halo of the sun”, was caused by interaction of sunlight with ice-crystals suspended in the cloud. “Known as 22° halo due to ring formation at exactly 22° from the sun at the centre, it happens when cirrus or cirrostratus clouds are formed in the upper troposphere at a height of 5-8 km from the earth surface during monsoon. The particular shape and orientation of the crystals are responsible for the type of halo observed,” said Birla Institute of Fundamental Research director (research and academic) Debiprosad Duari.

Scientists said the phenomenon wasn’t very rare and happened at different places, depending on the atmospheric conditions. The duration of the 22° halo of the sun depends on the cloud formations and the air currents.

In the evening, a rainbow, was visible to the east of the city and could be viewed from EM Bypass, New Town and adjoining areas.