The night sky could get three times brighter as new satellites launch — all but ruining the Vera C. Rubin Observatory’s survey of the universe
Constellations of Ultrabright satellites planned for launch over the next decade could make the sky three times brighter, threatening to ruin sky surveys like those planned for the new satellite. Vera C. Rubin Observatorywarns a new study. To avoid this, satellite operators will have to adhere to strict restrictions on size and brightness, according to the study uploaded to the preprint server. arXiv but has not been peer reviewed.
Thousands of satellites now hover over much of the Earth in vast constellations, and countless more are on the way. These satellites are already irritating astronomers, mainly by photobombing images of the sky.
However, the situation is set to get worse. As of April 2026, around 1.7 million satellites are expected to be launched over the next few years, according to a space sustainability expert. Jonathan McDowell noted on his website. Many are megaconstellations – groups of tens of thousands of satellites.
Some are problematic because the satellites themselves are large. These include AST SpaceMobile’s BlueWalker and BlueBird satellites, each of which is the size of a large studio and a tennis court, respectively. Other satellites, like those from Reflect Orbital — a controversial startup that plans to use giant space-based mirrors to produce solar power at night — will be highly reflective, making them appear like false stars in surveys.
These satellites could affect astronomical imaging in detrimental ways. On the one hand, the brightness of many satellites, combined with the low shutter speeds of astronomical cameras – designed to collect as much light as possible from distant celestial objects – can cause satellites to leave light trails in photographs.
The Vera C. Rubin Observatory sits atop a mountain in Chile.
(Image credit: Hernan Stockebrand)
“For some cameras… this causes a side effect (“saturation crosstalk”) which multiplies the effect of the light trail,” explained Hainaut. This could zap entire frames. Additionally, “light from bright satellites is scattered by the atmosphere, illuminating the entire sky,” Hainaut explained. “This constitutes light pollution.”
How bad could it be?
To determine exactly how the new satellites will affect observations, Hainaut created a computer model of how incoming visible light is scattered by Earth’s atmosphere.
This model took into account two physical phenomena causing the diffusion of light in the atmosphere. By accounting for both types of scattering, the model can map the appearance of the sky from any terrestrial observatory.
Hainaut focused on two instruments in Chile: a spectrograph at the Very Large Telescope and the Legacy Survey of Space and Time (LSST) camera at the Vera C. Rubin Observatory. To simulate the positions, brightness and movements of millions of satellites, he relied on an algorithm that he co-developed in 2022. study. With this comprehensive model, “I can say exactly how bad, in terms of costs and losses,” the proposed ultra-bright constellations and satellites could be, Hainaut said.
He found that a megaconstellation of 60,000 satellites (assuming all are less than magnitude 7) would contribute only 0.1% of the sky’s natural light. However, their trails would be problematic, saturating between 6% and 15% of the LSST camera’s field of view and erasing many observations.
Reflect Orbital plans to place up to 4,000 giant mirrors in low Earth orbit to reflect sunlight onto the night side of the planet.
(Image credit: Reflect Orbital)
Very large mobile broadband satellites would have an even more dramatic impact, even with a small number of satellites. For example, the 243 BlueBird satellites scheduled for launch will appear in images as dappled bright spots in the sky.
But the worst case scenario involves ultra-bright Reflect Orbital satellites. The model showed that a constellation of 50,000 of these satellites – similar to the company’s 2035 vision – could make the night sky three times brighter than it currently is, rendering images from the LSST camera worthless.
Restrictions may apply
Anthony Mallamaa researcher at the International Astronomical Union’s Center for the Protection of Dark and Calm Skies, who was not involved in the research, agrees with the findings.
“Bright satellites will have a significant impact on astronomy, even in moderate numbers,” Mallama told Live Science by email.
This also troubles Hainaut; he recommended that most satellites be less than magnitude 7. Mallama said operators can achieve this by applying a mirror-like coating to the satellites’ lower surfaces that would reflect any sunlight falling on those surfaces back into space. (Such techniques, however, cannot be applied to Reflect Orbital type satellites as this would defeat their purpose.)
Hainaut also believes that fewer than 10 satellites with magnitudes greater than 7 should be allowed in the sky at any one time. “A single bright satellite can cause more damage than thousands of faint satellites,” he said.
He recommended keeping the total number of satellites below 100,000. “It’s not a precise number,” Hainaut said. “But 100,000 causes [astronomical data] losses roughly equivalent to other technical losses, such as bad weather.
