The number of satellites orbiting Earth is growing at an incredible speed, and scientists say it could soon change the night sky forever.
A new study by the European Southern Observatory (ESO) warns that current plans to launch more than 1.7 million satellites could seriously harm astronomy and make it much harder to study the universe.
Today, more than 14,000 satellites orbit Earth, many of them belonging to SpaceX’s Starlink internet network.
However, several companies have announced plans to launch hundreds of thousands—or even millions—more satellites over the coming years.
According to the new study, modern astronomy could continue operating if Earth had no more than about 100,000 satellites that are too faint to be seen with the naked eye.
Beyond that number, the damage to astronomical observations could become severe.
Astronomer Olivier Hainaut, who led the research, says the situation is getting worse. Although some satellite companies have worked to reduce the brightness of their spacecraft, many future plans go far beyond what astronomers believe the night sky can safely handle.
One proposal from SpaceX includes sending one million additional satellites into orbit to support space-based data centers. Other planned satellite networks from companies in the United States and China would add hundreds of thousands more.
One of the most controversial ideas comes from the U.S. company Reflect Orbital. It wants to launch giant mirror-like satellites that would reflect sunlight onto Earth at night. The company hopes to build a fleet of 50,000 satellites by 2035.
According to the study, these mirror satellites would become the brightest objects ever placed in orbit.
If someone stood inside one of the reflected light beams, the satellite would appear four times brighter than the full moon. Even outside the beam, each satellite could shine as brightly as Venus, one of the brightest objects in the night sky.
The growing number of satellites creates two major problems for astronomy. First, satellites leave bright streaks across telescope images as they pass overhead.
These streaks can cover important objects such as distant galaxies, planets around other stars, or even asteroids that could one day threaten Earth.
The second problem is less obvious but just as serious. Light from thousands of satellites spreads through Earth’s atmosphere, making the entire night sky brighter. This extra glow makes it harder for telescopes to detect very faint objects in deep space.
Using computer simulations, the researchers found that some powerful telescopes could lose a large part of their observations every night. In some cases, future telescopes could have nearly all of their images ruined while satellites are illuminated by the Sun.
The study also points out that satellite mega-constellations may affect more than astronomy. Frequent rocket launches and satellite re-entry can pollute the atmosphere, while bright artificial light may disrupt wildlife, ecosystems, and even human biological clocks.
Scientists hope regulators will carefully examine these satellite proposals before approving them. They say low-Earth orbit is an important shared resource that supports communication, science, and many other technologies.
Protecting the night sky, they argue, will require cooperation between governments, satellite companies, engineers, and astronomers so future generations can continue exploring the universe without losing sight of the stars.
