Man-made objects orbiting the Earth have already brightened the night sky by 10%, far more than previously believed, new research has shown.
The new research means that Earth has already passed a threshold that was set by astronomers 40 years ago, meaning our planet is “light polluted”.
The researchers warn that the brightening of the sky is getting worse thanks to new satellite technologies such as ‘mega constellations’.
It could mean that star-gazers can no longer pick out iconic sights such as the clouds of the Milky Way, the researchers have warned.
The new research is the first to be based on the overall impact of space objects, rather than the effect of individual satellites.
The study included both functioning satellites, plus assorted debris such as spent rocket stages.
The research was published in Monthly Notices of the Royal Astronomical Society: Letters.
Miroslav Kocifaj, of the Slovak Academy of Sciences and Comenius University, said: "Our primary motivation was to estimate the potential contribution to night sky brightness from external sources, such as space objects in Earth's orbit.
“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."
While telescopes and sensitive cameras often resolve space objects as discrete points of light, low-resolution detectors of light (including the human eye) see only the combined effect of many such objects.
It means that the overall increase in brightness may obscure sights such as the glowing clouds of stars in the Milky Way, even away from the light pollution of cities.
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Study co-author John Barentine, director of public policy for the International Dark-Sky Association said, “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.”
“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.”
In recent years, astronomers have voiced unease about the growing number of objects orbiting the planet, particularly large fleets of communications satellites known informally as ‘mega-constellations’.
In the UK, the Royal Astronomical Society has established several working groups to understand the impact of mega-constellations on optical and radio astronomical facilities used by scientists.
Satellite operators like SpaceX have recently worked to lower the brightness of their spacecraft through design changes.
The researchers hope that their work will change the nature of the ongoing dialogue between satellite operators and astronomers concerning how best to manage the orbital space around the Earth.
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