In the clear skies of the Chilean desert, astronomers used to have a perfect view of the universe. They could trace the faint glow of galaxies billions of light-years away or hunt for brief flashes of an asteroid skimming past the Earth. Today, even in this remote sanctuary, streaks of light are scarring their images; bright lines painted by satellites racing across the sky.

“It’s becoming really an exponential thing, I think this is the problem here,” said Federico Di Vruno of the SKA Observatory, at the European Astronomical Society in Krakow, 2023, in a session dedicated to this issue. “The number of payloads in space is increasing like crazy,”

Astronomy, perhaps more than any other science, depends on what researchers call the “dark and quiet sky.” But that silence is being covered by satellite noise.

A New Kind of Pollution

When SpaceX launched its first batch of Starlink satellites in 2019, astronomers quickly realized they were facing a new era. At the time, there were only about 2,000 active satellites in low Earth orbit. By 2022, that number had already doubled. Today, there are more than 11,000, and plans for hundreds of thousands more. Yes, hundreds of thousands.

Most of these satellites are for internet. For millions of people on Earth, satellite internet can provide access to rural or remote areas where terrestrial cables aren’t feasible or reliable. But for astronomers, it’s a massive headache.

“To give you some perspective, we tracked four million conjunctions between satellites in 2022,” said Robert Massey of the Royal Astronomical Society, at the same meeting. “That’s a huge paradigm shift from where we were before.”

Satellites reflect sunlight as they orbit, appearing as bright moving streaks in telescope exposures. For sensitive surveys, like the upcoming Vera Rubin Observatory, these streaks can ruin entire observations. Twilight observations — the critical moments to spot asteroids that might one day threaten Earth — are especially at risk.

Invisible Threats

This isn’t just about academic or astronomical studies.

Believe it or not, we today know only about 90% of the asteroids that can have a big impact on our planet. When it comes to asteroids that can wipe out a city, we only know 20–30%. Astronomers are working to detect these dangerous objects, and satellites are affecting our ability to detect them.

It’s even worse for radio astronomy. This branch of astronomy studies celestial objects by observing the radio waves they emit or reflect. Satellites transmit broadband signals that can overwhelm the faint whispers of hydrogen gas from distant galaxies. Worse still, they leak what scientists call “unintended electromagnetic radiation” — random electronic noise from their onboard systems. In one study, Starlink satellites were measured to be 10 million times brighter than the faintest radio sources the LOFAR telescope could observe.

This is not catastrophic, Di Vruno said. “But we need to better observe it and understand it” to assess its effects.

Searching for Solutions

Companies like SpaceX have tried to dim their satellites with darker coatings or sun visors, producing versions known as DarkSat and VisorSat. These changes helped, but only modestly. The problem is scale: thousands of satellites still mean thousands of streaks, and most companies aren’t willing to pay extra to help our astronomers.

Mitigation in radio astronomy is even harder. Observatories are experimenting with algorithms to filter out interference and negotiating with companies to coordinate frequencies. One idea is for operators to temporarily power down parts of their systems when telescopes are observing. Operators could relinquish part of their system for a moment in time, but this requires coordination, goodwill, and isn’t simple to set up. But getting everyone on board with this is enormously challenging.

Regulation is also lagging behind. The International Telecommunication Union governs the radio spectrum, but its rules mainly apply to intentional emissions — not the accidental radiation spilling from satellites. That gap leaves astronomers with no legal tools to protect their work.

Still, there are glimmers of progress.

There Are Some Options

G7 science ministers recently signed a communique acknowledging “the impact of large constellations of satellites on astronomy for the protection of the dark and quiet sky.” The United Nations Committee on the Peaceful Uses of Outer Space has now put the issue on its agenda until 2029. And the International Astronomical Union has set up a dedicated center to monitor satellite impacts and push for new standards.

Yet this is more of a signal than practical action, and some of the most powerful tools remain unspoken.

Few policymakers have suggested placing hard limits on how many satellites can fill low Earth orbit, even though such caps are routine in other commons like fisheries or air traffic. Without a ceiling, technical patches will always be overwhelmed by sheer numbers. Others propose orbital “zoning,” where certain regions of the sky — or certain frequency bands — are reserved for science.

Transparency could also go much further. Companies might be required to disclose not only their planned transmissions but the levels of stray radiation their satellites produce, with mandatory pre-launch testing to ensure compliance. Such rules would not dim the night sky overnight, but they would give astronomers a fighting chance to plan, adapt, and preserve humanity’s oldest window to the cosmos.

The Stakes Are High

The debate over mega-constellations is not only about science. For much of humanity, the Milky Way is already hidden behind urban light pollution. If the skies become saturated with satellites, even remote dark sky parks will lose their purpose. There is intrinsic value of the star field, Massey says, and it’s under threat.

For astronomers, the danger is not just losing data, but losing discoveries. The most important breakthroughs often come from the unexpected: a new kind of supernova, the faint trail of a near-Earth asteroid, a strange radio burst from a distant galaxy. Those signals are fragile.

The satellites promise faster internet to the world’s most remote corners. But they also risk cutting us off from a cosmic heritage that has guided humanity for millennia.

The sky is not infinite. It is a commons, and one now being reshaped before our eyes.

Mega-constellations may connect villages and cities in ways never before possible. But unless we choose carefully, they could also disconnect us from the universe itself. The next great discovery — of a planet, a dangerous comet, or the first hint of life beyond Earth — may depend on whether we keep the heavens open, or allow them to be drowned in noise.

The sky belongs to all of us. The question is whether we will defend it.