Source: Royal Astronomical Society https://ras.ac.uk/news-and-press/news/satellites-contribute-significant-light-pollution-night-skies
by Robert Massey on Mon, 29/03/2021
Scientists reported new research results today suggesting that artificial objects in orbit around the Earth are brightening night skies on our planet significantly more than previously understood.
The research, accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters, finds that the number of objects orbiting Earth could elevate the overall brightness of the night sky by more than 10 percent above natural light levels across a large part of the planet. This would exceed a threshold that astronomers set over 40 years ago for considering a location “light polluted”.
“Our primary motivation was to estimate the potential contribution to night sky brightness from external sources, such as space objects in Earth’s orbit,” said Miroslav Kocifaj of the Slovak Academy of Sciences and Comenius University in Slovakia, who led the study. “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.”
The work is the first to consider the overall impact of space objects on the night sky rather than the effect of individual satellites and space debris affecting astronomers’ images of the night sky. The team of researchers, based at institutions in Slovakia, Spain and the US, modelled the space objects’ contribution to the overall brightness of the night sky, using the known distributions of the sizes and brightnesses of the objects as inputs to the model.
The study includes both functioning satellites as well as assorted debris such as spent rocket stages. While telescopes and sensitive cameras often resolve space objects as discrete points of light, low-resolution detectors of light such as the human eye see only the combined effect of many such objects. The effect is an overall increase in the diffuse brightness of the night sky, potentially obscuring sights such as the glowing clouds of stars in the Milky Way, as seen away from the light pollution of cities.
“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,” explained John Barentine, Director of Public Policy for the International Dark-Sky Association and a study co-author. “Astronomers build observatories far from city lights to seek dark skies, but this form of light pollution has a much larger geographical reach.”