Telescopes blinded by light
Astronomers say street lighting having ‘measurable’ effect on work in Atacama Desert
WHEN some of the world’s leading astronomers scaled a frosty Chilean peak last month to break ground on a state-of-the-art $1 billion (R14.94bn) telescope, they were stunned by an unexpectedly hazy glow.
On the floor of the Atacama Desert, about 1 700 metres below the planned Giant Magellan Telescope, new street lights lining Chile’s north-south highway shone brightly.
To the naked eye the Milky Way still looked sharp, but to a sensitive, state-of-theart telescope scouring the deepest reaches of the known universe, the new ground light could be blinding.
Guillermo Blanc, a University of Chile astronomy professor, who first saw the lights at the opening, said: “It’s like putting an oil rig in the middle of the Great Barrier Reef. It’s insane. Why are they trying to light up the Andes?”
Over the past 30 years, Chile has carved out a niche as the global hub for observational astronomy. More than a dozen major research telescopes have already been built, and by 2020 the South American country will have about 70 percent of the world’s astronomical infrastructure.
The low humidity and smooth airflow in northern Chile’s Atacama Desert create unrivalled visibility for the high-tech telescopes that scientists hope will shed light on the formation of the universe and the possibility of extraterrestrial life.
But scientists say light pollution has increased sharply in the barren Atacama as mining cities swell and tourist numbers mushroom.
Patrick McCarthy, the president of the Giant Magellan Telescope, which will be constructed at the Las Campanas Observatory in the southern Atacama, said: “There is an ongoing concern that ground-based astronomy is at risk long-term. There just are not that many pristine sites left. As these cities and highways grow, you start to wash out the faintest objects. The thing is, the faintest objects are the reason we’re building these telescopes in the first place.”
About 100km southwest of the Giant Magellan Telescope, the populations of Coquimbo and La Serena ballooned by almost 70 percent from 1992 to 2012. Nightclubs, sports arenas and sprawling suburbs spew bright, artificial light into the night sky.
Scientists at the Gemini Observatory, on an ochre mountain top more than 60km south-east of those cities, say increasing light pollution has already had a measurable effect.
René Rutten, an astronomer at Gemini, said: “You can already detect street lights at certain wavelengths. If you were to stand up here on a dark, moonless night you would see urban areas in the distance and even what you can see with the naked eye is very, very significant.”
The expansion of Route 41 linking La Serena to Argentina is another threat, said Chris Smith, Chile mission head for a Washington-based research group constructing the $665 million Large Synoptic Survey Telescope adjacent to the Gemini. If the proper measures are not taken, he said, light pollution could materially degrade the region’s skies in as little as a decade.
There are few official records of light pollution in Chile, and measuring it quantitatively over time is difficult. However, astronomers say artificial glow has increasingly bled from the horizon higher into the night sky in recent years.
Many scientists add that Chile’s skies still allow for excellent observations, but they complain that enforcement of toughened ground lighting regulations has been spotty. To take up the slack they are working directly with communities to build light fixtures that radiate only downward and at certain spectra.
While most nearby towns have been receptive, astronomers say, some business
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2015 lobbies complain of the potential impacts on industry, while local authorities have expressed safety concerns about darker streets.
Scientists have also asked the United Nations to label the region a World Heritage Site, a measure they hope will maintain the inky skies above.
Blanc said: “We’re trying to answer very fundamental questions: How did the universe begin? How did the sun form? That’s something that belongs to humanity and we think we have a duty, as a country, to protect it.” – Reuters