After the Boulder fire, a corona around the sun

Corona around the sun

Kathy Byrne in Boulder, Colorado, captured this image on the afternoon of January 2, 2022, just a few days after the devastating Marshall Fire in Boulder County burned more than 1,000 homes and other buildings. Kathy wrote:

It was fleeting but beautiful. It appeared only three days after terrible fires devastated nearby residential areas and seemed to offer some hope.

Les Cowley of the great website Atmospheric Optics told us that this photo shows a corona around the sun. Coronas are sometimes seen when thin clouds partially cover the sun or moon. Notice that the sun itself is behind the ridgeline for this photo; eye safety is important when viewing sun coronas. Kathy originally told us thought this image showed a sundog, but sundogs and coronas are different.

How to identify a sun corona

On his website, Les writes:

Coronas have an intensely bright central aureole which is almost white and fringed with yellows and reds. Sometimes that is all to be seen but the better coronas have one or more successively fainter and gently colored soft rings surrounding the aureole. The first ring is bluish on the inside grading through greens and yellows to red outermost. The colors are subtle mixtures rather than the more direct hues of the rainbow. The corona can be 15 degrees or so in diameter and often it shrinks and swells as different clouds scud across the moon.

We thought at first this might be a particular kind of corona, caused by pollen in the air. Our thought was that the fire might have caused pollen buds to burst, and that the pollen might have been kicked up by wind later on. But Les said “not necessarily.”

Thank you, Les and Kathy.

Marshall Fire Donations and Resource Center (Boulder Office of Emergency Management)

More Marshall Fire disaster aid resources (Boulder County)

Botton line: Corona around the sun, after the devastating Marshall Fire in Boulder County, early January 2022.

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