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Earth is running out of places for stargazers to do dark deeds in the name of science

A 'new deal for the night' needed

Increasing levels of light pollution means Earth's surface has almost no practical locations for astronomical observatories, a group of astronomers said on Monday.

Artificial light emitted from buildings, streetlights, and reflected from satellite constellations are making the night sky brighter for earth-bound skywatchers. The Milky Way was visible to pretty much everyone less than 100 years ago, but is now drowned out by human-made light to most, according to the International Dark Sky Association.

New ground-based telescopes are being built in increasingly secluded areas, but even in those out of the way locations a clear view of the dark sky is hard to find.

"Today, due to the rise of light pollution, there are almost no more remote places available on Earth that simultaneously meet all the characteristics needed to install an observatory (namely, the absence of light pollution, a high number of clear nights, and good seeing)," a team of astronomers said in Nature Astronomy

The authors urged astronomers, companies, politicians, and lawmakers around the world to work together to reach a global agreement to limit artificial light. Light pollution should be treated in the same way that other types of pollutants, like greenhouse gases, they argued. Governments around the world should and can tackle light pollution in the same ways they address climate change: with international treaties and goals to restrict levels of other pollutants. 

Another issue astronomers face is images snapped by cameras on telescopes being photobombed by satellites. A previous study conducted by astronomers in 2021 found that one in ten images are impacted by light streaks from passing satellites.

"Decided action should be taken in all countries, more urgently so in those who bear a larger share of responsibility in the present process of deterioration of the global night sky," they said.

SpaceX, for example, has reportedly launched nearly 4,000 broadband-beaming birds and plans to send tens of thousands more. The authors suggested that the US Federal Communications Commission or the Federal Aviation Administration could start assessing the impact and level of glare reflected from satellite constellations, for example. Similar restrictions could be placed on other satellite vendors in the US, UK, and China too.

The paper also calls for a limit on how dark the sky should be. Aerospace companies and space agencies could adopt strategies like deorbiting old spacecraft and getting rid of space debris before new constellations are launched or developing new techniques to make their satellites reflect less light.

Meanwhile, astronomers could build software to better control instruments and turn their cameras off when satellite constellations fly by. Or they could point their instruments at patches of sky free of human artifacts. 

"As it is not too late to stop this, we as scientists and first as citizens should act to stop this attack, from above with satellites and from below with [artificial light at night], on the natural night and on the intangible cultural heritage of humankind's starry skies," they concluded.

"Now is the time to consider the prohibition of mega-constellations and to promote a significant reduction in [artificial light at night] and the consequent light pollution. Our world definitely needs a 'new deal' for the night." ®

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