Categories: Astronomy

Satellites Have Brightened the Skies by About 10% Across the Entire Planet

An image of the NGC 5353/4 galaxy group made with a telescope at Lowell Observatory in Arizona, USA on the night of Saturday 25 May 2019. The diagonal lines running across the image are trails of reflected light left by more than 25 of the 60 recently launched Starlink satellites as they passed through the telescope’s field of view. Although this image serves as an illustration of the impact of reflections from satellite constellations, please note that the density of these satellites is significantly higher in the days after launch (as seen here) and also that the satellites will diminish in brightness as they reach their final orbital altitude.

New research has found that as the number of satellites in Earth orbit continues to increase, their accumulated light pollution will brighten the night sky – making it much harder to do fundamental astronomy.

The continued launch of so-called “mega-constellations” of satellites, used to power global internet access, has been met with concern by astronomers worldwide. Those astronomers worry that individual exposures of distant objects will be ruined by a satellite crossing in front of the telescope.

But new research recently appearing in the Monthly Notices of the Royal Astronomical Society paints an even more grim picture. As more and more satellites go up, they each contribute a small amount to the overall brightness of the sky, something called light pollution.

“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.”

If all the planned mega-constellations go up, within just a few years our sky will be 10% brighter across much of the planet. To estimate this result, the research team took into consideration the individual shape, reflectivity, and orbit of the satellites, as well as the contribution of random space junk, like spent rocket boosters.

The end result is that even the most pristine places on Earth, far away from any cities, will still suffer.

“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.”

The researchers hope that this will spurn satellite makers to take the worries of astronomers seriously, and continue to develop aggressive mitigation strategies.

“Our results imply that many more people than just astronomers stand to lose access to pristine night skies,” Barentine said. “This paper may really change the nature of that conversation.”