ESO study says proposed satellite megaconstellations could brighten the night sky and hinder ground-based astronomy
The Facts
- A new study by the European Southern Observatory says current proposals for satellite megaconstellations could have major negative effects on ground-based astronomy by brightening the night sky.
- The study says proposals now under discussion total more than 1.7 million satellites in low Earth orbit.
- The researchers say Earth currently has about 14,000 active or orbiting satellites, and that the total has risen rapidly since 2019.
- According to the study, keeping the total below about 100,000 satellites that are faint enough not to be visible to the naked eye would help preserve astronomers' ability to observe the night sky.
- The study is described as the first to estimate how much large, bright satellite constellations would affect astronomy by increasing overall sky brightness, beyond the already known problem of satellite trails crossing telescope images.
- The findings matter for observations of faint and distant targets, with sources saying brighter skies would make it harder for telescopes to detect objects such as distant galaxies, exoplanets and potentially hazardous asteroids.
- Companies cited in coverage of the study include SpaceX, which is linked to plans for up to 1 million additional satellites, and Reflect Orbital, which has proposed reflective satellites that would send sunlight to Earth at night.
- What happens next remains unresolved because the study presents a scientific threshold and warning, while the proposed satellite deployments would still depend on regulatory approvals and industry decisions.
Context
What is new in this study?
Multiple reports say the study is the first to calculate how much large, bright satellite constellations would affect astronomy by making the night sky itself brighter, not only by leaving streaks across telescope images Yahoo!,Dawn,La Presse.ca.
Why does a brighter night sky matter to astronomers?
A brighter background sky reduces contrast, making faint objects harder to detect. Sources say that would hinder observations of distant galaxies, Earth-like exoplanets and asteroids from ground-based telescopes LaVanguardia,Notícias ao Minuto,Earth.com.
What limit do the researchers propose?
The study says Earth orbit should stay below about 100,000 satellites, and that those satellites should be faint enough not to be visible to the naked eye from dark sites, in order to preserve the ability to observe the sky from Earth Deutschlandfunk Nova,LaVanguardia,Gizmodo.
Where Left and Right agree, and where they split
- Where Left and Right agree
- Proposals on the table would expand orbit far beyond a threshold the study says would better preserve astronomy, making brighter skies a real cost of satellite growth.
- Where Left and Right split
- Whether the story is about protecting a shared night sky and the science it enables, or about enforcing clear limits once researchers identify a threshold for harm.
How left and right read it
What stands out here is the scale mismatch between a rapidly growing orbital buildout and the public good it can degrade: a shared night sky and the ground-based science that depends on it. The study’s warning that proposals exceed 1.7 million satellites, while astronomy is better protected below about 100,000, matters because brighter skies would make it harder to detect faint, distant, and potentially hazardous objects.
A proposal to expand low Earth orbit from about 14,000 satellites to more than 1.7 million is exactly the kind of case where restraint matters, because the study says the result could be a brighter night sky and major harm to ground-based astronomy. When researchers can identify a threshold that would better preserve observation, approvals and industry decisions should treat that warning as a real limit, not an afterthought.
The receipts — all 66 sources
Wire services (1)
Independent coverage (50)
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