Astronomers worried by launch of five new super-bright satellites

An unusually reflective prototype satellite that outshines almost every star in the sky will be joined by another five later this week. Astronomers warn the appearance of more and more bright objects in the night sky will severely hinder their work and could even limit our ability to spot asteroids heading for Earth.

Texas-based AST SpaceMobile launched its first BlueWalker 3 satellite in 2022 and immediately drew criticism from astronomers who discovered that it was brighter than all but seven stars in the night sky.

AST SpaceMobile intends to launch a fleet of around 100 satellites in total to provide mobile phone connections around the globe. The reason for their unusual reflectiveness, which is far higher than most communications satellites, is that they include a 64-square-metre reflective antenna that inadvertently acts like a mirror for visible light.

The company said in a press release it was aiming to launch the first five commercial satellites, called BlueBirds, from Cape Canaveral, Florida, on 12 September. Last year, the company said it was exploring options to mitigate its impact on astronomy, but it didn’t respond to a request for interview from New Scientist about the latest launch.

Grant Tremblay at the Center for Astrophysics, Harvard & Smithsonian, in Massachusetts, who is vice-president of the American Astronomical Society, says the increasing number of constellations of satellites in low-Earth orbit “truly is an existential problem for astronomy”. While AST SpaceMobile is a concern to astronomers because of its incredibly reflective design, it is by no means the only one, he says. Internet firm Starlink is another company whose satellites have raised worries.

“For astronomy, things are absolutely tangibly getting worse,” says Tremblay. “I fear that we’re at risk of losing the sky.”

Projects such as the Vera C. Rubin Observatory, under construction in Chile and due to start scanning the sky in 2025, will have images spoiled by bright streaks when satellites cross their field of view, says Tremblay.

“When a frame is contaminated by, for example, a Starlink crossing, the frame is useless. You throw it out,” he says. “The observatory will still work. It’ll still do amazing science. But efficiency could drop off a cliff if we start heading into a regime in which hundreds or thousands of reflecting – this size or larger – satellites are in orbit. We are entering a completely unsustainable regime that has absolutely no regulatory structure.”

Tremblay believes this is a loss to science, but also to wider society. “We return images of this incredibly magical universe whose scale is truly unimaginable, and there’s something unifying in that, and inspirational in that. If we lose that, I think that’s a societal catastrophe.”

To solve the problem, he says astronomers may have to put more telescopes in space beyond our cluttered orbit, but the cost and complexity of doing that almost always makes it prohibitive.

Losing astronomical capabilities could even put humanity in danger, others have warned. Ian Carnelli at the European Space Agency says we have spent decades improving our ability to spot asteroids heading for Earth and potentially divert them with projects like NASA’s DART spacecraft. “It could be harder to find them in the future [because of reflective satellite constellations], for sure,” he says.