The recent launch of mega-constellations, such as Elon Musk’s StarLink, has been criticized for how their brightness and orbits affect current and upcoming ground-based observatories. But the situation appears to be worse than we thought. New results suggest that artificial satellites are contributing to more light pollution than previously thought.
The work, published in the Monthly Notices of the Royal Astronomical Society Letters, looked at the whole cloud of human-made objects that orbit our planet. This not only include active satellites, but also disused ones. It also includes parts of rockets and plenty of small fragments of space junk.
The individual and most sizable objects can only be captured by the sharpest instruments but as a whole, the unresolved clutter above us produces a glow that is brightening the night sky more than 10 percent above natural levels. This is beyond the threshold agreed in 1979 for when a location is to be considered light-polluted.
"Our results imply that many more people than just astronomers stand to lose access to pristine night skies. This paper may really change the nature of that conversation," co-author John Barentine, Director of Public Policy for the International Dark-Sky Association, said in a statement. “Unlike ground-based light pollution, this kind of artificial light in the night sky can be seen across a large part of the Earth’s surface. Astronomers build observatories far from city lights to seek dark skies, but this form of light pollution has a much larger geographical reach.”
The work is the first to consider the overall effect of artificial objects in space on the night sky. The team was not expecting it to be significant for the everyday observer but the analysis shows that it is a very important factor to consider going forward.
"Our primary motivation was to estimate the potential contribution to night sky brightness from external sources, such as space objects in Earth's orbit," explained lead author Miroslav Kocifaj of the Slovak Academy of Sciences and Comenius University in Slovakia. "We expected the sky brightness increase would be marginal if any, but our first theoretical estimates have proved extremely surprising and thus encouraged us to report our results promptly."
Private companies have started mitigating the reflectiveness of what they send to orbit but this might not be enough. The sharp increase of objects around the planet is dramatically changing what the night sky looks like.