Light pollution is brightening the sky so much that stars are “disappearing” from human eyes. The conclusion is from Globe at Night, a citizen science program that has collected data on stellar visibility for years. After analyses, researchers concluded that the artificial lights illuminated the sky faster for human eyes than the satellite data seemed to indicate.
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For the study, researchers from different institutions worked with data from 50,000 observations of the night sky with the naked eye, carried out by volunteers between 2011 and 2022 for the Globe at Night project. They focused on data from Europe and North America, as these regions had sufficient distribution of observations in the territory and period analyzed.
Then they developed a method for converting star observations into estimates of change in “sky brightness,” the name given to the diffuse illumination of the sky considered a form of nocturnal pollution. The study showed that brightness is increasing faster than shown in satellite data.
Satellite measurements indicated that the increase in light pollution was stable, and that it was even decreasing slightly in the most affected areas of the studied regions. After converting the loss of visible stars described in the project, the researchers found a 9.6% increase in sky brightness each year — until then, the increase was 2%, a number coming from satellite data. This suggests that previous estimates are likely to be wrong.
“Satellites are most sensitive to light directed upwards towards the sky, but it is light emitted horizontally that causes most of the glow,” said Christopher Kyba, lead author of the paper describing the results. “At this rate of change, a child born in a place where 250 stars were visible will be able to see about 100 of them by the time they reach 18,” he warned.
The results show that the sky is getting brighter at different rates around the world — in North America, for example, sky brightness increases by more than 10% each year. Finally, the team notes that a shortcoming of the study is the lack of sufficient data from developing countries, where changes in sky illumination may be happening at an even faster pace.
It may not seem like it, but the decrease in darkness is a worrying problem not only for astronomers and astronomy enthusiasts. Constance Walker, co-author of the study, points out that unrestricted exposure to light affects both humans and animals. “Sky glare affects both diurnal and active animals, and also destroys an important part of our cultural heritage,” Walker said.
The article with the results of the study was published in the journal Science.
Source: Science; Via: NOIRLab