Scientists worry that the high reflectivity can pose a problem for astronomical observations
If you look up in the night sky, you can see satellites with bare eyes. That fascinating phenomenon, 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 the new Amazon Leo satellites exceed recommended brightness and could disrupt astronomical research.
The study analyzed 1,938 observations of Leo satellites orbiting at 630 km, and found that they have an average magnitude of 6.28. For perspective, the faintest star in the sky has a magnitude of 6. This makes the satellites faintly visible from Earth, but their intermittent light flares tend to create noise for telescopic data.
IAU’s brightness standard states that satellites should remain below magnitude 7 to avoid interference with telescopic data, and below magnitude 6 to preserve the natural aesthetics of the night sky.
With Leo, “92% exceeded the brightness limit recommended by the IAU for interference with research, while 25% distract from aesthetic appreciation of the night sky,” the study found.
Amazon’s plan to lower Leo satellites to 590 km could partially address the issue. At lower altitudes, satellites are less visible during a single pass. However, observers below the orbital path are 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. “They also distract from aesthetic appreciation of the night sky”. The trails tend to distort astronomic images and are significantly costly to repair.
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 (5,500 satellites) which start deployment in 2027. What happens when these reach their operational orbit?
Mallama cautioned that the number of deployments could directly scale 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 have higher magnitudes. 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 the brightest objects in the sky, thanks to their colossal antennas (690 sq ft and 2,400 sq ft). But, their overall impact is much lower due to the 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 repositioning the reflective underside to reflect sunlight 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 the interference. The company said it is “applying a custom dielectric film and non-reflective coating on all of our operational spacecraft,” to dim the shine.
“We’re encouraged by the initial results of that work and expect to continue improving as more satellites reach assigned altitudes. We’ll continue to invest in this research and development, and look forward to continuing our work with the scientific community to learn and iterate further,” they said.
