Artificial satellites are changing the night sky at an unusual pace, according to a new peer-reviewed study by the European Southern Observatory (ESO). Published in the journal Astronomy & Astrophysics, the research warns that proposals to launch more than 1.7 million satellites into low-Earth orbit could permanently transform humanity’s view of the cosmos. The study finds that rapidly expanding satellite mega-constellations would significantly brighten the night sky, interfere with ground-based telescopes, and create a persistent veil of artificial light that threatens astronomical discoveries.

With over 14,000 active satellites already orbiting Earth compared to fewer than 2,000 just a decade ago, the report calls for urgent international regulation before Earth’s orbital environment reaches an irreversible tipping point.

Satellite Numbers Are Growing at an Unusual Rate

• Since 2019, the number of operational satellites has increased dramatically, largely driven by SpaceX’s Starlink broadband network.
• However, the ESO study warns that the next generation of proposed satellite constellations would be far larger than anything currently in orbit.
• Researchers examined planned deployments from companies and organizations, including SpaceX, E-Space, China’s CTC networks, and Reflect Orbital, whose proposed fleet of 50,000 mirror satellites would intentionally reflect sunlight onto Earth during nighttime hours.

According to lead author Olivier Hainaut, modern astronomy can remain viable only if the total number of low-Earth orbit satellites stays below 100,000 and they remain too faint to be seen with the naked eye.

How Mega-Constellations Affect Astronomy

The study explains that artificial satellites are changing the night sky in two major ways:

First, bright satellites leave luminous streaks across telescope images as they pass overhead. Simulations using ESO’s Very Large Telescope (VLT) in Chile suggest that the planned SpaceX constellation alone could reduce usable observations by up to 28% just two hours after sunset.

The impact is even greater for highly sensitive observatories like the Vera C. Rubin Observatory in Chile. Bright satellite reflections can overload camera sensors, creating “ghost trails” that may render entire astronomical images unusable.

Researchers warn that a single mirror satellite from Reflect Orbital could ruin one observation, while the complete constellation could interfere with virtually every nighttime exposure when illuminated by the Sun.

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The Growing Problem of Artificial Sky Glow

Beyond visible satellite trails, scientists identified a less obvious but equally serious concern: diffuse sky glow.

• Millions of satellites, even those too faint to be individually detected, collectively scatter sunlight through Earth’s atmosphere, making the entire night sky brighter.
• The study estimates that Reflect Orbital’s planned mirror constellation alone could increase global background sky brightness by three to four times.
• This additional brightness makes it significantly harder for astronomers to detect faint celestial objects such as distant galaxies, Earth-like exoplanets, and potentially hazardous near-Earth asteroids.

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Calls for Global Regulation

Recognizing the long-term risks, the European Southern Observatory, together with the International Astronomical Union (IAU) and the Royal Astronomical Society, has submitted formal interventions to the U.S. Federal Communications Commission (FCC), which oversees several major satellite licensing applications.

Public concern is also growing: The FCC has received more than 1,800 public comments regarding Reflect Orbital’s proposal and nearly 1,500 comments related to SpaceX’s expansion plans.

Scientists argue that low-Earth orbit should be treated as a shared global resource requiring coordinated international governance rather than unrestricted commercial development.

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