Light pollution is reducing views of the night sky for many

Light pollution is reducing views of the night sky for many

If you have even a passing interest in astronomy, chances are good that you have considered the problem of light pollution. As there are more and more sources of bright light at night on Earth, it becomes more and more difficult to see the stars in the sky. But a recent analysis has pointed out that the problem could be worse than anticipated, since what is visible to the human eye is even less than what satellite measurements indicate.

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 new research shows that the problem is getting worse.

Light pollution infographic from Globe at Night.
A startling analysis from Globe at Night, a citizen science program run by NSF’s NOIRLab, concludes that stars are disappearing from human sight at a staggering rate. This graph illustrates how the greater the amount of light pollution, and therefore the brightness of the sky, the fewer stars are visible. The numerical scale is similar to that used by Globe at Night participants. NOIRLab/NSF/AURA, P. Marenfeld

The research, published in the journal Science, was led by the citizen science group Globe at Night. It found that the brightness of the night sky had increased by a global 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 by volunteer participants who share information about which stars and constellations are visible to them and exclude conditions such as cloudiness. Lead author of the Science paper, Christopher Kyba, says this shows how satellite measurements of light pollution are not enough to capture the scale of the problem.

Today’s satellites cannot see shorter wavelengths of light that are typically used by energy efficient white LEDs. “Since human eyes are more sensitive to these shorter wavelengths at night, LED lights have a strong effect on our perception of sky brightness,” Kyba explained. “This could be one of the reasons behind the discrepancy between the satellite measurements and the sky conditions reported by Globe at Night participants.”

This means that views of the night sky, which are important to everything from professional astronomy to amateur stargazing to 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 were seen might only see about 100 by the time they turn 18,” Kyba said.

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