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Earth Notes: Wildfire Smoke and Telescopes

An aerial view of an open telescope dome surrounded by pine forest.
Lowell Observatory
The Lowell Discovery Telescope Dome in Happy Jack, Arizona.

The Environmental Protection Agency has been working to improve air quality across the U.S. for more than 20 years.

Arizona Department of Environmental Quality data shows the average concentration of fine airborne particulate matter in the state has decreased by nearly 20% since 2012.

But smoke from wildfires can offset those improvements for short periods. Not only can smoke cause health risks for residents... it’s a cause of concern for astronomers, too.

Microscopic particles in smoke — known to scientists as PM2.5 — are 20 times smaller than the diameter of a human hair. They include "black carbon," a type of soot that comes from the incomplete burning of gasoline, diesel, wood and living biomass like trees.

For people, not surprisingly, breathing in smoke — especially black carbon — can increase the risk of heart disease and asthma, and adversely affect brain function and mental health.

But you might be surprised to learn that particles in smoke are bad for telescopes too! They scatter light, obscuring fainter objects in the night sky, plus sensitive optics can be damaged by the particles settling on them.

In Flagstaff, Lowell Observatory monitors air quality and will typically shut down its telescopes if the Air Quality Index exceeds 100 — that’s 100 micrograms of particles in every cubic meter of air. But even such a seemingly tiny amount can pose potential risks to both humans and the telescopes they use to explore the universe.

This Earth Note was written by Diane Hope and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.

Diane Hope, Ph.D., is a former ecologist and environmental scientist turned audio producer, sound recordist and writer. Originally from northern England, she has spent much of the last 25 years in Arizona and has been contributing scripts to Earth Notes for 15 years.
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