Smoke From US Wildfires Is Turning the Moon an Eerie Color

Few locations this week have been spared the encroaching haze from the more than 80 wildfires presently burning in the American West. An area of high pressure across the U.S. prevented smoke from dissipating into the upper atmosphere and instead pushed it down to the surface; inundating the air of cities more than 3,000 miles away and setting off health advisories and poor air quality alerts. 

"As long as active fires are burning and high pressure remains across the central part of the United States, many locations will at least see some reduction of visibility in their environment east of the Rockies," Julie Malingowski, an emergency response meteorologist with the National Weather Service, told NPR.

As shown in the below map of black carbon particulates (aka, soot) from NASA, the scale of those impacted (as of July 21st) is astonishing. 

Not surprisingly for anyone who spied the sun this week looking like an angry red ball glowing through the haze, astronomers are expecting the wildfire smoke to also lend some unusual colors to this weekend’s rising full moon. Leading up to peak fullness tomorrow evening, people on social media are already posting photos of their reactions to the moon’s deep orange or reddish-hue. 

Rise of the Thunder Moon

This month’s full moon, nicknamed by some indigenous tribes the “Thunder Moon” in recognition of mid-summer’s stormy reputation, will rise on July 23 and reach peak fullness at 10:37 p.m. EST. This full moon has also been nicknamed the Buck Moon (for when deer begin growing their antlers), the Ripe Corn Moon, and the Hay Moon. Europeans also called it the Meade Moon as it coincided with an uptick in honey harvest for making the delicious drink.

So why are wildfires causing the moon to glow this eerie red? Hannah Seo over at Popular Science offers this great explanation: 

“The red skies in the aftermath of a fire are due to smoke particles interfering with how sunlight travels through the air,” she writes. “Light comes in a spectrum of wavelengths. Fire smoke blocks out the shorter wavelengths of blues, greens, and yellows, while allowing the longer waves of red and orange through. Since the glow of the moon is just reflected sunlight, smoke interferes with moonlight as well.”

If you’re reading this and remembering a time when you saw a blood red moon without any air quality woes, you likely spied it during a lunar eclipse. This phenomenon occurs when the moon briefly crosses through the Earth’s shadow (or umbra). The filtered light that is cast upon the lunar surface is remarkably the culmination of every sunrise and sunset on Earth. 

“The red is the projection of all the sunrises and sunsets onto the lunar surface,” Dr. Noah Petro, a project scientist for NASA, told Forbes. “We see it turn red not because of some mythical fire-breathing dragon, but because of the properties of the Earth’s atmosphere scattering light.”

That the moon is flaring red this weekend for some of us is less a spectacle and more a grim reminder of the terrible events occurring out West. Let’s hope it’s back to its usual golden hue when next it rises full on Aug. 22.