Odd glows around sun may be caused by Canadian forest fires

A large, pale blue aureole or disk surrounds the sun this morning July 18 in a sky filled with high-altitude smoke from forest fires burning in Canada’s Northwest Territories. Wide-angle 15mm lens view. Credit: Bob King

It happens every summer. Forest fires in Canada pump out vast quantities of smoke which are carried by winds to the south and east. Arriving days later over the northern Great Plains and Midwest, the blue sky soon turns a pallid gray.

Smoke from forest fires near Faber Lake in the Northwest Territories streams south in this photo taken July 7, 2014 by NASA’s Terra satellite. Credit: NASA

The smoke spreads in subtle ripples and bands and dims sun and stars alike. Technically, the sky is clear, and that’s what you’ll hear from the weather service, but the smoky haze creates an overcast of its own. Sunlight is less intense, while the solar disk glows pale yellow-orange compared to its normal white-yellow. It may even disappear from view well before sunset, fading away in the fiery haze.

Wide-angle photo this morning showing the blue aureole and brownish outer ring around the sun. Could smoke particles be responsible for the appearance? Credit: Bob King

Early this morning, under faux clear skies, I noticed an unusual pale blue disk or aureole around the sun about four fists (40 degrees) wide. Beyond that lay a wide, darker ‘ring’ tinted a pale gray-brown. Forest fires release gobs of minute smoke particles and oil droplets into the atmosphere which, like the ash from volcanic eruptions, can occasionally color the sun or moon blue.

Patches and bands of smoke from forest fires are seen in this National Weather Service satellite photo taken this morning July 18, 2014. Credit:NASA

It works like this. Particles that are about 1 micron across (1/1000 of a millimeter) are the same size as the wavelength of red light. The sun pours out all colors of light, but when the red portion strikes the ash or smoke, it’s scattered about the sky. The shorter wavelength blue light isn’t affected and continues to pass directly to our eyes, coloring the sun a pale blue. In effect, the particles act like a blue filter.

Bishop’s Ring around the sun due to volcanic ash of the Eyjafjallajökull volcano on Iceland. Photographed from Leiden, the Netherlands on May 18, 2010. Credit: Marco Langbroek

I’ve seen no blue moons or suns yet, but I wonder if the blue aureole might be the result of smoke particles. It resembles a phenomenon called Bishop’s Ring seen around the sun during volcanic eruptions and created by ash and sulfur droplets. Notice though the ball of the sun remains red-orange, indicating that the smoke particles are not the right size to create a blue sun. At least not yet.

A red sky sunset Friday evening July 18. Colors are enhanced from airborne smoke. Credit: Bob King

If you live where the sky is affected by the smoke of distant fires, keep an eye on the sun, moon and sky for unusual colors, disks and rings. We’d love to hear what you’re seeing.

Abundant high altitude dust on Mars scatters red light away from the sun, lending both the solar disk and sky near it a pale blue. Photo taken on May 19, 2005 by the Spirit Rover. Credit: NASA/ JPL-Caltech

My blue disk this morning also reminded me of the blue aureole around the rising sun on Mars taken by the Spirit Rover. Dust in the Martian atmosphere scatters red light like much like ash and fire smoke do on Earth. Blue sunrises and sunsets there are probably fairly common.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

3 thoughts on “Odd glows around sun may be caused by Canadian forest fires

  1. Bashing Canada seems to be the trend. First, it was the blizzards cold fronts and Alberta clippers. Then, the polar vortex. Today, smoke from the mostly naturally caused wildfires.
    TV shows such as South Park & My Name Is Earl got some ratings boosts from laughter at the expense of Canada, on the surface reserved and polite.
    Little do our American friends know that since June 1948 (August 1814 was just a warning), the Canadian government has used a lot of resources to implement a plan that will soon be too late to stop. Documents obtained through the freedom of information process show in details the “cold”conspiracy at work. It can all be viewed here: http://youtu.be/XEaFLdK_e64
    As they say in Québec: Nous Vaincrons ;)

  2. As a British Columbian, I can assure my U.S. neighbours that we are not so paranoid about TV comedies or by weather reports and forest fire reports in the news as to think we are being “Bashed” by them. As for our present Government’s using “a lot of resources to implement a plan that will be too late to stop” showing “in details the ‘cold’ conspiracy at work”, the facts are that our current Government is the “conspiracy at work” that is forcing damaging legislation through Parliament that undermines science-based efforts to address climate change, is ignoring Canadian public opinion by attempting to force through environment-destroying cross-country oil pipelines to carry toxic bitumen from the Alberta Tar Sands to the Pacific Coast for export to China, and has slashed government research funding and muzzled Federal scientists from publicly reporting their research findings. The present government labels any criticism of its destructive behaviour as government bashing and has been assiduously working to fulfill its promise to.”make Canada unrecognizable when it completes its agenda.”

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