Satellites and space debris are increasing the brightness of the night sky by at least 10 percent over natural light levels, exceeding a threshold set by astronomers in 1979 defining a location as “light polluted,” according to a new study published by the Royal Astronomical Society. The International Astronomical Union defines light pollution as “artificial light that shines where it is neither wanted, nor needed.” That includes not only light created by cities, but by the more than 9,200 tons of objects now orbiting Earth that reflect or scatter sunlight.
Satellites have long been a nuisance for astronomers, since they periodically photobomb long-exposure images, appearing as streaks of light. This new study, however, uses a model to estimate the overall impact of orbiting objects. Researchers found that, collectively, this reflected sunlight has the same effect as ground-based light pollution by making it “difficult to see faint astronomical objects by lowering the contrast between objects and the sky itself,” says astronomer John Barentine, one of the study’s authors. But what makes it more worrisome is its geographic reach. Says Barentine: “There’s nowhere, except the polar regions, where this kind of light pollution really can’t be seen. That’s especially important for astronomical observatories, which now are built far from cities at great expense.”
And it’s a problem that could get worse as more satellites are launched and orbital collisions threaten to create more debris.