On the top of a mountain in the Chilean desert, an $800 million U.S.-taxpayer-funded telescope just opened its eye.

The brand-new Vera C. Rubin Observatory is supposed to complete a groundbreaking “survey” of the universe, the most comprehensive catalog of its galaxies, asteroids, supernovas and black holes ever completed. But Rubin’s scientists have encountered a problem. Fast-moving, light-reflecting satellites are leaving white streaks across their photographs.

The proliferation of satellites is an “existential threat” to the observatory’s work, said J. Anthony Tyson, its chief scientist, who is best known for mapping dark matter.

Tyson and other scientists warn that these orbiting machines will make it increasingly difficult to do astronomical research from Earth—and, eventually, will render the night sky unrecognizable.

Currently, there are more than 17,000 active satellites in orbit, compared with around 1,000 a decade ago, said Jonathan McDowell, an astrophysicist who has cataloged every orbital rocket launch since 1957. A decade from now, he estimates, there will probably be over 100,000.

Satellites reflect sunlight back to Earth. As the number of satellites grows, so too will light pollution from space.“You’d see twice as many stars in the sky,” said Hanno Rein, an associate professor at the University of Toronto who has modeled light pollution from planned satellite constellations.

“But only half of them would be real.”The other half would actually be satellites transiting the sky.

Currently, satellites are mainly used for telecommunications. The majority are owned by Starlink, which provides internet connectivity around the world.

In the future, as it becomes cheaper to launch material into space, more companies and governments will launch their own satellites. Blue Origin, Google, Cowboy Space and others have all said they plan to build orbital data centers, which would likely consist of hundreds of thousands of satellites. SpaceX says its “Starmind” orbital data center would have over a million satellites.

Satellites now aren’t very large. Starlink’s satellites are about four square meters in size, roughly equivalent to a king bed. But satellites involved in orbital data centers would be much larger. SpaceX said in public filings that the satellites involved in its orbital data center would be up to 1,500 square meters. Cowboy Space said its satellites would be 4,800 square meters, close to the size of a football field.

SpaceX has voluntarily mitigated the brightness of its Starlink satellites, Tyson said. He has been discussing brightness mitigation with SpaceX staffers for almost a decade. Another Rubin scientist said it has had “positive dialogues” with a half-dozen other satellite companies. “They’ve been very helpful, or they’re trying to be,” he said. But Starlink satellites are already brighter than International Astronomical Union recommendations and visible to the unaided eye, he said. Tyson hasn’t talked to any Chinese satellite manufacturers. Chinese satellites are sometimes brighter than American ones, scientists said.

SpaceX didn’t respond to requests for comment. Google and Blue Origin declined to comment. Cowboy Space couldn’t be reached for comment.

The FCC approves satellite projects, though it doesn’t have any rules about how bright satellites can be. “With the exception of a U.S. law preventing space-based advertising, there are no laws regulating the visual appearance of the night sky” anywhere in the world, stated a 2022 Dark and Quiet Skies Working Group report that reviewed satellite regulations across the globe.

Companies plan to make their orbital data centers “sun-synchronous,” which means they would almost always be illuminated by the sun, said Samantha Lawler, an associate professor at the University of Regina who recently co-wrote a paper about light pollution from orbital data centers.

These solar-powered satellites would reflect even more sunlight back onto earth than other satellites do. Lawler estimates they would be as radiant as Venus, already one of the brightest points in the sky. Collectively, hundreds of thousands of these satellites would probably “completely drown out” the Milky Way and dimmer stars at certain times of night, Lawler said.

Shane Ross, an engineering professor at Virginia Tech, recently created a model of what SpaceX’s orbital data center would look like from Earth. His projection shows a belt of thousands of bright points, stretching from horizon to horizon, moving slowly across the night sky.A 12-second recording shows what an orbital data center could look like from Earth approximately an hour after sunset in December in the Northern Hemiphere at 10x speed, according to Shane Ross’s recently created model.

Credit: Shane Ross, Virginia Tech“It’s awesome, but it’s kind of unsettling,” he said.

When he shared the projection, reactions varied. “Some people were really excited about this,” he said. “Others said we were ruining some common heritage of humankind.”

Tyson and his fellow astronomers at the Rubin Observatory just started their 10-year survey of space. Now, he wonders if they’ll be forced to end the experiment early. Not only do satellites leave streaks across the telescope’s photographs, but Tyson also projects that megaconstellations of satellites would scatter so much light that it would brighten the entire sky. Eventually, “the sky would be too bright to do anything,” Tyson said.

Write to Rebecca Cadenhead at rebecca.cadenhead@wsj.com