In this dawning age of artificial intelligence, tech companies are racing to train and run their large language models using massive data centers that guzzle electricity and strain resources. Even among those who rely on AI-powered tools, these data centers are deeply unpopular—proposals to build new ones are increasingly met with the familiar refrain of “not in my backyard.” To dodge those concerns and offload environmental costs, some entrepreneurs plan on building solar-powered data centers in orbit. But megaconstellations of such satellites could completely transform the night sky, astronomers report in a paper posted to the preprint repository arXiv.org on August 3.

“People have lost the sense of the night sky because of the light-polluted cities, and now we’re rewriting that story with artificial satellites,” says Aaron Boley, an astronomer at the University of British Columbia and the study’s lead author. If the most ambitious megaconstellation plans go through, sunlight reflecting off the satellites’ large solar arrays would create an inescapable fixture of lights at dawn and dusk, visible from the most remote “dark sky” locations and even the most light-polluted cities.

Orbital data centers are not a far-fetched hypothetical. Aerospace heavyweights such as SpaceX and Blue Origin—as well as ambitious, well-capitalized start-ups such as Cowboy Space Corporation—have filed proposals with the U.S. Federal Communications Commission (FCC) for data center constellations consisting of anywhere between 20,000 to one million satellites. The most efficient—and thus the most sought-after—orbit for these satellites would circle Earth’s poles along the cusp between day and night, where they could receive constant sunlight from our star.

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To better understand the associated impacts on the night sky, Boley and his colleagues modeled the optical brightness of three orbital data center configurations proposed by different companies: Cowboy Space’s single satellite ring, Blue Origin’s crisscross of two satellite rings and SpaceX’s combination of crisscrossed rings and an additional shell of satellites circling Earth. The researchers also considered the spacing between satellites. A looser spread of objects would reduce collisional risk but sweep over greater portions of the sky, creating a widespread blanket of light as opposed to distinct rings.

Regardless of the configuration, the team’s modeling showed that the proposed satellites would profoundly change the night sky. Observed from lower latitudes, the orbital parade of satellites would peak in brightness at sunrise and sunset; toward the poles, the constellations would be bright and visible for most of the night during winter and the equinoxes. Without careful planning to reduce the constellations’ brightness, the team found that, in the most extreme case, the satellites could outnumber visible stars by a factor of 100.

For astronomers, these satellites would become a nightmare for observations, crowding out and obscuring fainter objects or even challenging the Milky Way’s prominence with their glare. The effects would be especially disruptive in Antarctica, where observatories take advantage of the continent’s remote, dry conditions and the round-the-clock darkness of polar winter to study subtle signals such as the cosmic microwave background. Heat emissions from the satellites would also interfere with infrared observations, and their communications with ground stations or other spacecraft could pose problems for radio astronomy. Even space telescopes would be affected by satellites regularly photobombing their fields of view.

Astronomers and satellite companies have collaborated to mitigate some of these effects; for example, SpaceX and the National Radio Astronomical Observatory (NRAO) coordinate via a data-sharing system so that NRAO radio telescopes avoid collecting data when Starlink satellites pass overhead. But depending on the megaconstellation’s configuration, the sheer abundance of satellites might make avoiding them impossible, the study found.

Megaconstellation-sourced light pollution could also have environmental effects, disrupting animals that rely on cues from dark skies to survive. “Currently, light pollution is concentrated in cities,” says Gaspar Bakos, an astronomer at Princeton University, who was not involved in the current study. “The effect of satellites is truly global, with no place to retreat from them.”

Whether all satellite operators will rise to the occasion by voluntarily limiting the brightness of their megaconstellations remains to be seen. SpaceX has promised to adopt mitigation strategies in their filings, but other companies have not publicized plans for any mitigation efforts, and the FCC has declared that light pollution from satellites is, by and large, not under its control. Instead “public pressure has helped steer companies toward investing in brightness mitigations,” Boley says. “It could be a lot worse right now if astronomers weren’t speaking up and studying the issue.”

This struggle reflects the larger tension between technological progress and environmental sustainability. Orbital data centers may be billed as a panacea for reducing stress on Earth’s resources, but any spaceward shift will not actually address the root of those problems—and will introduce new ones—Boley argues. “And so what can we do to try to minimize those impacts?” he says. “Those are questions that we should be asking ourselves.”