Light pollution prevents many from seeing the night sky

Light pollution prevents many from seeing the night sky

If you have even a passing interest in astronomy, chances are good that you have thought about the problem of light pollution. As more and more sources of bright light appear on Earth at night, it becomes more and more difficult to see the stars in the sky. But a recent analysis has shown the problem could be worse than thought, as what the human eye can see is even smaller than what satellite measurements show.

According to the National Science Foundation’s NOIRLab, about 30% of the world’s population and 80% of the US population can no longer see our Milky Way galaxy. And a new study shows the problem is getting worse.

A startling analysis of Globe at Night, a citizen science program run by NSF’s NOIRLab, concludes that stars are disappearing from human vision at an astonishing rate. This graph shows how the greater the amount of light pollution, and therefore the glow of the sky, the fewer visible stars. The digital scale is similar to that used by Globe at Night members. NOIRLab/NSF/AURA, P. Marenfeld

The study, published in the journal Science, was led by the Globe at Night science team. The brightness of the night sky has been found to have increased by an average of 9.6% per year over the past decade, much worse than the 2% increase obtained from satellite measurements. The Globe at Night figure is based on data collected by volunteer participants who share what stars and constellations they see, excluding conditions such as cloud cover. Lead author of the paper, Christopher Kiba, says this shows that satellite measurements of light pollution are not enough to capture the scale of the problem.

Current satellites cannot see the shorter wavelengths of light that power-saving white LEDs typically use. “Because human eyes are more sensitive to these shorter wavelengths at night, LED lamps have a strong effect on our perception of sky brightness,” Kiba explained. “This may be one reason for the discrepancy between satellite measurements and sky conditions reported by Globe at Night participants.”

This means that the views of the night sky, which are important for everything from professional astronomy to amateur stargazing and cultural and religious practices regarding the stars, are under threat for many.

“At this rate of change, a child born in a place where 250 stars are visible will only be able to see about 100 by age 18,” Kiba said.

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