The International Astronomical Union (IAU) has concluded a scientific review of satellite mega constellations such as SpaceX’s Starlink, and warns that they could have “” consequences for astronomy. The organisation is calling for new rules to protect the night sky.
The IAU began studying the problems posed by mega constellations following concerns after the launch of SpaceX’s first batch of 60 Starlink satellites in May 2019. The satellites are designed to beam high-speed internet around the world, but the first launch also resulted in many artificial bright points of light in the sky.
SpaceX is set to perform its fifth Starlink launch on 15 February, bringing its total number of satellites to 300. The firm plans to launch thousands more, as do competitors such as OneWeb in the UK.
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“When all this started we were of course worried by the situation, but we wanted to be scientific in our evaluation of the impact,” says Piero Benvenuti at the IAU.
The findings showed that mega constellations would have a “negative impact” on astronomy. Olivier Hainaut from the European Southern Observatory, who led one of the studies, simulated 26,000 satellites at various altitudes. Of those, he found that about 1000 would be visible to telescopes at dawn or dusk, when the sun is below the horizon but the satellites are still illuminated.
Telescopes conducting large surveys of the night sky, such as the upcoming Vera C. Rubin Observatory in Chile, could stand to lose up to 50 per cent of their images at this time as a result, with the large number of satellite trails rendering observations useless. “Survey telescopes would be really badly affected by these constellations,” said Hainaut.
However, the impact on naked eye astronomy would be “small”, says Hainaut, once the satellites are in their operational orbits – they are more visible immediately after launch, because they clump together when deployed at lower altitudes. He calculates that only about 10 satellites would be visible to the naked eye at any one time from dark locations on Earth. “We’re talking about a handful of objects,” he says.
Nonetheless, the IAU says the night sky “should be considered a non-renounceable world human heritage”, and hopes to draw up new limits on satellite brightness. In the next year they plan to submit their guidelines to the United Nations, says Benvenuti, in an effort to have new rules in place.
“We have to be very fast, because these private companies are moving much faster than the space agencies,” he says.
SpaceX is expected to launch 1500 satellites this year, while OneWeb is aiming for 400. Both firms didn’t respond to requests for comment.
