Space pollution: astronomers sound the alarm due to the spread of satellites

The sky is darkening for astronomers. Space pollution caused by the spread of satellites in orbit is interfering with telescope observations to the point of threatening the future of the profession, astronomers warn in a study released Monday.

Since 2019, the number of satellites has more than doubled due to megaconstellations, these constellations of satellites sent by, among others, the US company Space X, and projects to deliver broadband from space are multiplying. This colonization of low orbit (altitude up to 2000 km) overloads traffic, increasing the risk of collisions. As a result of a chain reaction, these collisions create more and more debris, which itself turns into smaller and smaller fragments, increasing the cloud of debris that gravitates over our heads.

The implications are “dramatic” for professional astronomy facing an “unprecedented” transformation of the night sky, according to this study, published in the journal Nature Astronomy. By reflecting sunlight, satellites amplify the effect of light pollution from the ground. Some companies, including Space X, have also tried to reduce the brightness of their machines to reduce these inconveniences. But the impact of small debris is even more problematic: Telescope images are polluted by the many light trails they produce, while “the light reflected from the debris continues to brighten the sky,” according to John Barentin, co-author. -author of the study. “We want to get rid of light pollution, and we end up seeing thousands of satellites,” said Eric Lagadec, an astrophysicist at the Côte d’Azur-UCA observatory who was not involved in the research.

As light pollution on earth continues to rise, places suitable for building telescopes are shrinking, which several researchers lament, furthermore in papers attached to the studies. But the phenomenon goes beyond science and affects humanity’s “hereditary relationship” to the firmament, which should be seen as humanity’s “intangible heritage,” says astrophysicist Aparna Venkatesan of the University of San Francisco. “The loss of darkness, which affects even the summit of K2, the shores of Lake Titicaca or Easter Island, poses a threat to both the environment and our cultural heritage,” the astronomers, who turned to the scientific community, were alarmed.

Decrease in the number of observed stars

For the first time, astronomers have attempted to measure the reduction in observational efficiency due to this pollution and estimate the costs. Major scientific projects are affected, such as the Vera-C.-Rubin Observatory (VRO), a giant telescope under construction in Chile: models predict a 7.5% increase in zenith sky brightness over the next decade. However, even from a place free of light pollution, such as VRO, a 7.5% increase in sky luminosity would reduce the number of observed stars by the same amount, John Barentine calculates.

This will add “nearly a year to the nominal duration of the program, with an estimated additional cost of $21.8 million,” develops John Barentine. That’s a lot more than “the time and money we’re already wasting with other hazards like the weather,” laments the researcher at the American University of Utah. And the consequences could be even worse because current measurements of light pollution underestimate the phenomenon, another Nature Astronomy study points out.

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Another price: the loss of the ability to detect rare and unknown astrophysical phenomena. Some of them, such as meteor showers, are so subtle that they require absolutely clear skies to observe them.

To stop this “madness”, their authors call for a sharp restriction or even a ban on megaconstellations, emphasizing that all other “mitigating” measures will be ineffective. But “it is naïve to believe that the market for launchers will be regulated without restrictions,” given the economic interests at stake, they conclude.