Why are satellites a global threat?

Astronomers have warned that light pollution caused by the increasing number of satellites orbiting the Earth poses an “unprecedented global threat to nature”.

The number of satellites in low Earth orbit has more than doubled since 2019, when the US company SpaceX launched the first “huge constellation” of thousands of satellites.

A fleet of new internet clusters is due to be launched soon, adding thousands of satellites to the already crowded area of ​​less than 2,000 kilometers (1,250 miles) above Earth.

Each new satellite increases the risk that it will collide with another Earth-orbiting object, creating more debris.

This can create a chain reaction in which successive collisions create smaller fragments of debris, adding to a cloud of “space junk” that reflects light back to Earth.

In a series of papers published in the journal Nature Astronomy, astronomers warn that this increased light pollution threatens the future of their profession.

The researchers also said that for the first time they have measured how much a brighter night sky could financially and scientifically impact the work of a major observatory.

The modeling suggested that for the Vera Rubin Observatory, a giant telescope currently under construction in Chile, the darkest part of the night sky will become 7.5 percent brighter over the next decade.

This would reduce the number of stars the observatory can see by about 7.5%, study co-author John Barentyn said. “That would add nearly a year to the observatory’s survey, at a cost of about $21.8 million.”

And there is another cost to a brighter sky that is impossible to calculate, he added: celestial events that humanity will never be able to observe.

And the increase in light pollution may be worse than thought.

Another study in Nature used extensive modeling to suggest that current measurements of light pollution significantly underestimate this phenomenon.

This and the researchers warned that the brightness of the night sky will not only affect professional astronomers and major observatories. It also threatens our “age-old relationship with the night sky,” said Aparna Venkatesan, an astronomer at the University of San Francisco.

“Space is our common heritage and ancestor – connecting us through science, storytelling, art, origin stories and cultural traditions – and now it is in danger,” she said in a comment to Nature.

A group of astronomers from Spain, Portugal and Italy called on scientists to “stop this attack” on the natural night.

And he called on astronomers to radically limit the huge constellations, adding that “we must not reject the possibility of banning them.” They said it would be naïve to hope that the rising space economy would limit its expansion unless it was forced to do so, given the economic interests that would be at stake.