Astronomers could face growing difficulties observing the cosmos as thousands of new satellites enter orbit, according to a study by the European Southern Observatory (ESO), which operates telescopes in northern Chile.
The ESO study found that current proposals to launch more than 1.7 million satellites into orbit, including some very bright ones, would substantially harm astronomical work. There are currently about 15,000 satellites in orbit.
Bright trails of light left by satellites can interfere with the operation of observatories and the quality of night-sky photographs. ESO astronomer Olivier Hainaut, who authored the study published in the journal Astronomy & Astrophysics, said each satellite leaves a bright line as it crosses a telescope's field of view.
Small trails, growing problem
A single streak of light may be a minor nuisance, Hainaut said, but as the numbers multiply, serious problems can emerge. Each trail obscures a small part of a telescope's view of space, he said.
The global satellite industry has grown dramatically since 2019, driven by internet services such as Elon Musk's SpaceX Starlink and Amazon's Leo. Both companies operate large satellite constellations that provide broadband internet from low Earth orbit.
The study's findings were based on simulations carried out at the Paranal Observatory in Chile's Atacama Desert. One model examined a constellation of up to one million satellites, showing thousands of illuminated objects visible above ESO's Very Large Telescope (VLT) in the Atacama shortly after sunset.
How many satellites is too many
Hainaut said the impact would depend on both the number and the brightness of satellites in orbit. He said a level of 100,000 satellites would be a sustainable level of impact, but that at 300,000, some telescopes could be deprived of most of their data.
Despite the concerns, the researchers said the benefits of satellite internet services should not be minimized, and that the challenge lies in balancing technological progress with scientific discovery.
Hainaut added that the problem is that this kind of research takes time, while the satellites are already being launched.
