Ultrabright satellite constellations planned to launch in the next decade could make the sky three times brighter, threatening to ruin all-sky surveys like those planned for the new Vera C. Rubin Observatory, a new study warns. To prevent this, satellite operators will have to follow strict size and brightness restrictions, according to the study, which was uploaded to the preprint server arXiv but has not been peer-reviewed.

Thousands of satellites hover over much of Earth today in vast constellations, and countless more are on the way. These satellites are already vexing astronomers, mainly by photobombing images of the sky.

However, the situation is set to worsen. As of April 2026, roughly 1.7 million satellites are planned to be launched in the next few years, 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 about the size of a large studio apartment and a tennis court, respectively. Other satellites, like those of Reflect Orbital — a controversial startup that plans to use giant, space-based mirrors to generate 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. For one, the brightness of many satellites, coupled with astronomical cameras' low shutter speeds — designed to collect as much light as possible from distant celestial objects — may cause the satellites to leave bright streaks in photographs.

"For some cameras … this causes a secondary effect ('saturation cross-talk') that multiplies the effect of the bright streak," Hainaut explained. This could zap whole images. Additionally, "the light from the bright satellites is scattered by the atmosphere, illuminating the whole sky," Hainaut said. "This constitutes light pollution."

How bad could it be?

To determine exactly how new satellites will affect observations, Hainaut created a computer model of how incoming visible light gets scattered by Earth's atmosphere.

This model took into account two physical phenomena that cause light to scatter in the atmosphere. By accounting for both kinds of scattering, the model can map the sky's appearance from any Earth-based observatory.

Hainaut focused on two instruments in Chile: a spectrograph from the Very Large Telescope and the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) Camera. To simulate the positions, brightness and movements of millions of satellites, he drew on an algorithm that he co-developed in a 2022 study. With this comprehensive model, "I can say exactly how bad, in terms of cost and losses," the proposed constellations and ultra-bright satellites may be, Hainaut said.

He found that a megaconstellation of 60,000 satellites (assuming all were dimmer than magnitude 7) would contribute just 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.

Extra-large mobile broadband satellites would have an even more dramatic impact, even with a small number of satellites. For instance, the 243 BlueBird satellites scheduled for launch will appear in images as bright blotches speckled across the sky.

But the worst-case scenario involves superbright Reflect Orbital-type satellites. The model showed that a constellation of 50,000 of these satellites ‪—‬ similar to the company's 2035 vision ‪—‬ may make the night sky three times as bright as it is now, rendering the LSST Camera's images worthless.

Restrictions may apply

Anthony Mallama, a researcher at the International Astronomical Union's Centre for the Protection of the Dark and Quiet Sky who wasn't involved in the research, agreed with the findings.

"Bright satellites will significantly impact astronomy even in moderate numbers," Mallama told Live Science via email.

This troubles Hainaut, too; he recommended that most satellites be fainter than magnitude 7. Mallama said operators can achieve this by applying a mirror-like coating to satellites' lower surfaces that would reflect any sunlight falling on these surfaces into outer space. (Such techniques, however, cannot be applied to Reflect Orbital-type satellites because that would defeat their purpose.)

Hainaut also believes fewer than 10 satellites with a magnitude brighter than 7 should be permitted in the sky at one time. "A single bright satellite can cause more harm than thousands of faint ones," he said.

He recommended keeping the total satellite number under 100,000. "This is not a hard number," Hainaut said. "But 100,000 causes [astronomical data] losses at about the level of other technical losses," such as bad weather.