For many, light pollution limits the view of the night sky

For many, light pollution limits the view of the night sky

If you have even a passing interest in astronomy, chances are you’ve researched the problem of light pollution. As there are more and more bright light sources on Earth at night, it becomes increasingly difficult to see the stars in the sky. However, recent analysis has suggested that the problem could be worse than expected, as what is visible to the human eye is even less than satellite measurements have indicated.

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

Light pollution infographic from Globe at Night.
A startling analysis by Globe at Night — a citizen science program run by NSF’s NOIRLab — concludes that stars are disappearing from human sight at an amazing rate. This graph shows that the greater the light pollution, and therefore the glow in the sky, the fewer stars are visible. The numeric scale is similar to that used by the Globe at Night contestants. NOIRLab/NSF/AURA, P. Marenfeld

The study, published in Science journal, was led by citizen science group Globe at Night. It found that the world’s night sky had increased in brightness by an average of 9.6% per year over the past decade, which is far worse than the 2% increase found in satellite measurements. The Globe at Night figure comes from data collected from volunteer participants who share information about which stars and constellations are visible to them while excluding conditions such as cloud cover. The Science paper’s lead author, Christopher Kyba, says this shows that satellite measurements of light pollution are insufficient to capture the magnitude of the problem.

Current satellites cannot see shorter wavelengths of light that energy-efficient white LEDs typically use. “Because the human eye is more sensitive to these shorter wavelengths at night, LED lights have a powerful impact on our perception of sky brightness,” explained Kyba. “This could be one of the reasons for the discrepancy between satellite measurements and the sky conditions reported by Globe at Night participants.”

This means that viewing the night sky, essential to everything from professional astronomy to amateur stargazing to cultural and religious practices related to the stars, is under threat for many.

“At that rate of change, a child born in a place where 250 stars are visible might only see about 100 by age 18,” Kyba said.

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