September 28, 2023

The number of satellites in orbit is about to sky-rocket, and that could have serious consequences for astronomers, according to a new study.

In a race to provide low-cost internet to remote areas, companies like SpaceX are crafting plans to launch satellite “mega-constellations” — groups of satellites that communicate with one another — that enable the broadband technology.

It was widely reported last year that SpaceX alone had secured approval to launch 12,000 satellites as part of its StarLink constellation, pending approval of another 30,000.

That’s a sharp jump from the 5,500 satellites currently in orbit, which are tracked by the European Space Agency.

Other companies like Amazon and the U.K.-based OneWeb, have plans to launch thousands of their own satellites.

Now, new research from the European Southern Observatory (ESO), an astronomical research group, is raising an alarm about how these objects could disrupt ground-based observations of the night sky.

“Another blow to astronomy”: A Canadian astrophotographer and other stargazers weigh in on how satellites are affecting a pristine night sky.

The study, which will be published in the journal Astronomy and Astrophysics, looked at 18 satellite constellations under development worldwide, assuming a total of 26,000 satellites — a “conservative” estimate based on publicly available information.

It found that the greatest impact would be on wide-field surveys conducted by large telescopes, such as the Vera C. Rubin Observatory in Chile. It says 30 to 50 per cent of their exposures could be “severely effected,” depending on the time of year.

“These are engines of discovery for astronomy,” Andrew Williams, a co-author of the study told Spoke.

Wide-field surveys are often used to find points of interest, such as stars or galaxies, that merit further research, he explained.

Around 19 StarLink satellites (which appear as lines) were imaged shortly after launch in November 2019 by astronomers Clara Martínez-Vázquez and Cliff Johnson. (Credit NSF’s National Optical-Infrared Astronomy Research Laboratory/CTIO/AURA/DELVE)

Other large telescopes ESO uses to focus on small points of the sky would only have about 3 per cent of their exposures affected during twilight hours.

The study notes satellites can also be visible to the naked eye just before sunrise and after sunset when they are illuminated by sunlight, which has prompted many astronomers to brand them as a form of light pollution.

“For the average person, the problem of light contamination from satellites is nothing compared to the problem of light contamination just from other sources like cities,” Williams said.

But while it’s possible to escape light contamination by moving to a remote location or with special filters, satellites are a virtually permanent fixture, he said.

To lessen the impact of satellites, ESO says they can change the operating hours of their telescopes, although that comes at a price. They suggest the aerospace industry should also work to darken satellites.

At a March 9 conference in Washington, D.C., SpaceX founder Elon Musk said that the company’s satellites wouldn’t impact astronomical discoveries.

Although it wasn’t in the study itself, Williams says that the lack of international rules surrounding the nature of satellites contributes to the problem.

“How big it is, how bright it is, this is not regulated at all,” he explained.

“There is no law an astronomer can turn to.” 

The study notes that more research needs to be done to precisely quantify the impacts on astronomy, because it is based on several simplifications and assumptions, such as the total number of satellites that will be in orbit in the near future.

It’s also only valid for satellites that operate at low- to mid-latitude — about 30 degrees from the horizon.

Further studies will also need to be done to find the effects on different kinds of telescopes.

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