The night sky has always been a source of wonder and discovery. But as satellites increasingly populate low Earth orbit. While SpaceX’s Starlink satellites may dazzle stargazers with “trains” of glinting lights after launch, an invisible menace follows in their wake: radio frequency pollution, and it’s threatening to blind our most sensitive ears to the universe.
On clear nights, people across the globe have marveled at the sight of Starlink satellite, a phenomenon known as a Starlink train streaking across the sky shortly after launch. These formations eventually disperse into SpaceX’s growing megaconstellation, a network that aims to provide global internet coverage. But there’s a less visible consequence to this orbital expansion: unintended electromagnetic radiation, or UEMR, a kind of radio leakage that threatens to drown out the faint signals from the farthest reaches of space.
“If our eyes could see radio waves,” the article notes, “the sky would be full of bright spots and nonstop flashing.” Unlike visible light interference, which is often brief and nighttime-limited, UEMR is continuous and all-pervasive.
Radio telescopes, like the massive LOFAR in the Netherlands and China’s FAST, are uniquely designed to pick up weak cosmic whispers from black hole jets and distant quasars, to elusive fast radio bursts and ancient galactic echoes from the dawn of time. But these signals lie within the same frequency ranges now being polluted by satellites, particularly those in private hands like Starlink.
Benjamin Winkel, a radio astronomer at the Max Planck Institute, voiced a stark warning: “It would mean that no radio astronomy from the ground would be possible anymore.”
Indeed, researchers are concerned we’re approaching an “inflection point” — a threshold beyond which Earth-based radio astronomy could become obsolete.
As of mid-2025, over 11,700 satellites orbit Earth, 60% of them part of Starlink’s fleet, all launched since 2019. Looking ahead, over a million more satellites are proposed, and experts estimate that low Earth orbit might soon support as many as 100,000 satellites. These devices aren’t just sending intentional signals back to Earth; they’re constantly leaking unintended radiation — UEMR — into space.
In 2023, a study using LOFAR found that Starlink’s Gen 1 satellites leaked significant amounts of UEMR in the 110 to 188 MHz range. But a 2024 follow-up revealed an even graver reality: “The newer Generation 2 Starlink satellites were leaking over 30 times more UEMR than their predecessors,” despite prior warnings to SpaceX.
These signals are not subtle. The leaked radiation from Gen 2 satellites is up to 10 million times brighter than the faintest radio sources astronomers seek to study, akin to photographing the stars. At the same time, someone shines a flashlight directly at your camera.
The result? Sensitive radio bands may soon become unusable. As Federico Di Vruno from the SKA Observatory explained: “Some radio bands could be completely wiped out… it would mean that we are effectively closing ‘windows’ to observe our universe.”
Long-term observations, crucial for phenomena like pulsar timing or cosmic microwave background studies, are especially vulnerable. As Winkel noted, “Even tiny interference signals can have a statistical impact on the results.” Cleaning polluted data is an option, but it’s costly and risks erasing valuable information. “The more interference, the more data you must discard,” Winkel said.
There are strategies on the table. Some companies are experimenting with boresight avoidance, pausing transmissions over observatories. Space agencies like NASA already minimize UEMR far better than private firms. But once a satellite is launched, fixing leaks becomes almost impossible.
Regulation is desperately needed. Currently, the International Telecommunication Union (ITU) protects radio frequencies on Earth, but not in orbit. UEMR remains unregulated, even as it overlaps with protected bands. Fionagh Thomson, a space ethics researcher, warns that existing ITU standards are outdated: “They were set in a different era and are arguably too narrow for modern radio astronomy.”
The International Astronomical Union’s CPS is pushing for tighter controls, ideally by 2027. But even with new rules, enforcement remains uncertain. As Thomson puts it, “There is an assumption that imposing laws will fix complex problems… But not all viable solutions involve implementing binding legislation.”
Meanwhile, NASA is eyeing more radical alternatives, including a giant radio telescope on the moon’s far side, where Earth’s noisy satellite environment can’t interfere.
