Light Pollution: What Is Brightening Our Night Skies?

Above is an image showing Berlin at night. Crerdit: Image Science & Analysis Laboratory / NASA Johnson Space Center

Walking through neighborhoods, volunteers identified sources of light pollution —surprisingly, streetlights weren’t the main culprit.

If you’ve noticed your night sky becoming brighter over recent years, you’re not imagining things: Studies from the ground suggest that the amount that artificial light spills into the atmosphere is increasing by 10% year over year. We were supposed to see the opposite effect. Yet conversion of streetlights to energy-efficient LEDs, often fully shielded to direct light toward the ground, somehow weren’t doing the trick.

Using a simple app — and the help of hundreds of citizen scientists — a research group led by Christopher Kyba (Ruhr University Bochum, Germany) has found out the cause of this discrepancy. Publicly controlled streetlights only make up only a small percentage of contaminating light sources. The vast majority of light-pollution sources are private and commercial windows and signs, which so far have hardly been studied, let alone regulated.

(Source: skyandtelescope.org)