California is on fire. Hundreds of wildfires across the state are filling the air with smoke and filling the sky with ... lavender suns? Christopher Calubaquib saw one on June 26th when he looked through the haze over El Sobrante, California:

Purple sun
©Christopher Calubaquib

"Because of the smoke, the sun was not very bright. I didn't need to use a filter," says Calubaquib. A day later, another lavender sun appeared over Arcata, California:

©Mike Kelly

"The colors were not retouched; that is how it really looked," says photographer Mike Kelly.

What makes the sun lavender? It happens when the air is filled with particles measuring about 1 micron (10-6 m) across, a little larger than the wavelength of red light. Micron-sized particles scatter red light strongly, while letting shades of blue pass through. The mix of ash over El Sobrante produced a lavender hue, reminiscent of the great Alberta muskeg fires of September 1950. Believe it or not, the same physics can turn the Moon blue, but that is another story.

Is the smoke wafting through your hometown this weekend? Be alert for the lavender sun.