Michael Calkins, a science technician at the Fred Lawrence Whipple Observatory, has spent nearly two decades observing Tucson’s star-studded night sky. Lately, he has had a growing fear that one of the country’s best vantage points of the stars is under threat from a new neighbor 13 miles away.
Rosemont Copper, a Canadian-owned mining company, is in the process of developing an open-pit copper mine. It will be one of the largest copper mines in the United States. Light pollution caused by the mine’s powerful artificial lights, which the astronomy community says will reduce Whipple Observatory’s ability to continue observing and discovering.
“Light pollution is just light going where it wasn’t intended,” said Richard Green, a professor of astronomy at the University of Arizona. “And in our case, that’s light mostly that ends up in the sky that creates artificial glare in front of the celestial objects we would like to observe.”
Mr. Calkins, to demonstrate his point that this new mine is a threat, drove his motorcycle up Mount Hopkins, ascending nearly 9,000 feet to the Fred Lawrence Whipple Observatory, which operates the third-largest optical telescope in the country. He was surrounded by optical, spectroscopic and multiple-mirror telescopes that help the scientists there study not only stars, but also supernovae, exoplanets, spectral gamma-ray bursts and the galaxy itself.
“The public has to be aware that every photon that goes up has a good chance of landing right here in our telescope,” Mr. Calkins said.
The proposed mining project will run 24 hours, which requires the installation of a lot of lighting for miners. The multiple observatory telescopes can pick up contaminants or light changes in the sky beyond the human eye’s capability, Mr. Calkins said.
Rosemont’s most recent lighting plan would produce six million lumen (a unit of measure of light), according to its website. This is a significant difference from its initial light plan, which would have produced more than 20 million lumen.
The company said it is trying to minimize light impact and preserve Arizona’s dark skies.
“You need good light out there at night when you’re working around heavy equipment in the pits and processing facilities,” said David Briggs, a geologist who has done consulting work for the Rosemont mine and has worked in mining for more than 35 years in Arizona.
“Tucson is really the copper-producing capital of North America,” he said. “It’s important to Tucson’s economy. It brings jobs to the local economy.”
Rosemont is voluntarily complying with the Pima County Outdoor Lighting Code, even though it is bound by federal regulations, Mr. Briggs said.
Decades ago, the Whipple Observatory’s site was selected because of its mountaintop location, clear skies and isolation from city lights — a setting conducive to observations, said Richard Green, a professor of astronomy at the University of Arizona.
“A light right next door to me has the equivalent impact of something a hundred times brighter that’s 10 times farther away,” Mr. Green said.