Rare Parhelic Circle and Other Optical Phenomena Seen Around the Sun in England

TEMPO.CO, Jakarta – An astronomer in England recently recorded a halo and a series of glowing arcs around it sun in the sky. Included in his enshrinement was an extremely rare ring of light that encircled the sky.

Alan Fitzsimmons, astronomer at Queen’s University, Belfast, Northern Ireland, captured the unusual light show from the Belfast Botanical Gardens on May 28, 2023. “The show lasted about 30 minutes,” said Fitzsimmons. Phenomena similar to those seen by Fitzsimmons have also been reported in other parts of Northern Ireland, as well as northern England and Scotland.

Fitzsimmons said the halos and arcs of light are caused by millions of tiny ice crystals perfectly positioned in Earth’s upper atmosphere, which often accompany wispy cirrus clouds. “If the wind up there is very uniform, the hexagonal-shaped crystals align,” he said, adding that sunlight refracted through the crystals produced the halos and arcs of light.

The photos obtained from Fitzsimmons include at least three different optical phenomena. First, a 22 degree halo, the great circle around the sun. Then, a pair of “sundogs”, bright spots on each side of the halo. And finally, the complete parhelic circle, the line that bisects the halo, which also makes a full circle around the entire sky.

Full parhelic circles are extremely rare because they require at least five internal reflections from millions of individual ice crystals, all catching sunlight simultaneously. It is a white horizontal circle with the same angular elevation as the Sun.

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Bright spots can be observed at certain points of the parhelic circle. These spots most often appear slightly beyond the 22 degree halo (parhelia, often brightly colored).

Occasionally, a bright spot (paranthelia) is seen at an azimuth distance of 120 degrees from the Sun and, very rarely, opposite the Sun (anthelion). When the parhelia, paranthelia or anthelion are very bright, they are often called mock suns.

Similar phenomena produced by the Moon are called paraselenic circles, paraselenae, parantiselenae, and antiselene. When paraselenae, parantiselenae or antiselene are very bright, they are sometimes called artificial moons.

The parhelia and paraselenae are sometimes connected by a 22 degree halo with obliquely oriented Lowitz bows.

Lowitz arcs are a relatively rare cluster of halos beyond the 22 degree halo. They are only visible when the Sun’s altitude is high.

A closer look at the photo can also include halo features and supralateral arcs, which form the “eyelids” above and below the 22 degree halo.

“Pahelic circles are the rarest and most impressive features in images,” said Fitzsimmons. The circle was an object he had seen only a few times before. But another phenomenon is more common than most people realize.

“The sun can be very bright when [fenomena] visible, so to see it, you need to block the sun with your thumb or a tree,” said Fitzsimmons. “But anytime it’s clear with light clouds high up, it’s good to see if there’s a halo or perhaps something more.”

Then, on May 30, a photographer in Finland also managed to photograph a rainbow-colored halo, known as a pollen corona, that surrounds the sun. These rings, which are created by the scattering of light from airborne pollen grains, are also hard to spot unless some of the sunlight has been blocked.

Tiny atmospheric ice crystals can also create a series of other unique visual phenomena, such as polar stratospheric clouds, which glow like rainbows over the North Pole, and clouds that glow at night, also known as noctilucent clouds. These clouds will be more visible to people in the northern hemisphere poles during June and July.

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