Star visibility eroding rapidly as night sky gets brighter: Study

Light pollution is growing rapidly and in some places the number of stars visible to the naked eye in the night sky is being reduced by more than half in less than 20 years, according to a study released on Jan. 19.

The researchers, whose findings were published in the journal Science, said the increase in light pollution, skyglow, that they found was much larger than that measured by satellite observations of Earth at night.

For the study of the change in global sky brightness from artificial light, the researchers used stellar observations from 2011 to 2022 submitted by more than 51,000 "citizen scientists" around the world.

Participants in the "Globe at Night" project run by the U.S. National Optical-Infrared Astronomy Research Laboratory were given star maps and asked to compare them to the night sky at their location.

The change in the number of visible stars reported was equivalent to a 9.6 percent per year annual increase in sky brightness, averaged over the locations of the participants, the researchers said.

Over an 18-year period, given such star brightness change, a location with 250 visible stars would see that number reduced to 100.

Most of the naked-eye star observations came from Europe and the United States said Christopher Kyba, one of the authors of the study, but there was also good participation in Uruguay, South Africa and Japan.

"The global trend in skyglow that we measure likely underestimates the trend in countries with the most rapid increases in economic development, because the rate of change in light emission is highest there," the researchers said.

The study coincided with the replacement of many outdoor lights with light-emitting diodes (LEDs), but the researchers said the impact...