Scientists worry that Leo’s high reflectivity can pose a problem for astronomical studies
If you look up in the night sky, you can see satellites with bare eyes. That fascinating phenomenon now has become a cause of worry for the scientific community.
Astronomers at the International Astronomical Union (IAU) Centre for the Protection of the Dark and Quiet Sky found that new Amazon Leo satellites exceed recommended brightness and could disrupt astronomical research.
IAU’s brightness guidelines state that satellites should remain below magnitude 7 to avoid interfering with telescopic data, and below magnitude 6 to preserve the natural aesthetics of the night sky.
The study analyzed 1,938 observations of Leo satellites orbiting at 630 km, and found that they have an average magnitude of 6.28. Which means, to bare eyes, they are only dimly visible from Earth, but their intermittent light flares are bright enough to create noise in telescopic data. For context, the faintest star in a clear night sty registers at magnitude 6.
The study concluded “92% exceeded the brightness limit recommended by the IAU for interference with research, while 25% distract from aesthetic appreciation of the night sky.”
Amazon’s plan to place new satellites at a lower orbit of 590 km could partially solve the issue as the satellites will be less visible during a single pass. However, observers below the orbital path will be then more likely to see them.
A problem of too many
With satellite constellations proliferating at a rapid clip, astronomers are becoming increasingly uneasy about what it could mean for scientific work.
“Bright satellites interfere with astronomical research by leaving streaks across photographic images,” Anthony Mallama, lead author of the paper, said in an email. The trails tend to distort space images and are significantly costly to repair.
“They also distract from aesthetic appreciation of the night sky,” he added.
The brightness impacts not only ground-based observatories, but also those in space like the Hubble Space Telescope.
With thousands of satellites set to deploy in 2026, the problem might get bigger. Currently Leo has 180 satellites in orbit, with plans to send up over 3,000 more for the first constellation. Add to that the 7,500 satellites SpaceX just secured regulatory approval for — and Blue Origin’s TeraWave fleet of 5,500 satellites which starts deployment in 2027.
What happens when these reach their operational orbit? Mallama warned that the number of deployments could directly scale the impact. “More satellites mean more light pollution in the night sky,” he said.
Not an isolated instance
Leo’s brightness problem is not an isolated instance. Mallama and his peers have studied satellite brightness of other providers in the past and found that Starlink and AST SpaceMobile assets have even higher magnitudes than Leo. But, luckily for Starlink, the satellites remain in the Earth’s shadow for a majority of their orbital time, which naturally reduces their reflectiveness.
AST’s BlueBird satellites are by far the brightest man-made objects in the sky, thanks to their colossal antennas (690 sq ft and 2,400 sq ft). But, their overall impact is still low due to their smaller fleet size.
Both SpaceX and Amazon are working with the scientific community to address the issue. Amazon told RCR Wireless News, “Space safety and sustainability have always been key considerations for the Amazon Leo team, and we’ve made several design and operational decisions to help reduce our impact on astronomical research.”
One of the ways operators can cut the glare is by positioning the reflective underside of satellites in a way that it bounces sunlight back into the space instead of scattering it to the ground. “They can also orient satellite components so that observers on the ground don’t see the sunlit sides,” Mallama said.
Amazon has been collaborating with the U.S. National Science Foundation (NSF) on engineering to minimize Leo’s interference. The company said it is “applying a custom dielectric film and non-reflective coating on all of our operational spacecraft,” to reduce reflectivity.
“We’re encouraged by the initial results of that work and expect to continue improving as more satellites reach assigned altitudes,” the company said.
Editor’s note: This article has been updated with revised information.
