Bright Artificial Satellite Shines in Night Sky Raises Astronomy Concerns
Researchers from the International Astronomical Union have highlighted the BlueWalker 3 satellite, a prototype operated by AST SpaceMobile, as one of the most luminous objects observed in Earth’s orbit. They warn that such bright artificial structures could interfere with astronomical measurements and long-term sky surveys. This assessment appeared in the scientific record through Nature, emphasizing the potential impact on observational astronomy.
BlueWalker 3 features a substantial 63 square meter dish antenna that unfolds to a size large enough to be seen from Earth when in orbit at about 500 kilometers above the planet. The satellite was launched in September 2022 and, once the antenna fully deployed, its reflective surface began to radiate light with an apparent magnitude of approximately 0.4. In practical terms, this places the device among the brighter celestial views visible at night, surpassing many familiar stellar references in brightness.
To understand this brightness, brightness scales for stars assign lower numbers to brighter objects, and extremely luminous bodies can carry negative values. For example, the Sun registers at -27, while Sirius shines at about -1.46. In this context, BlueWalker 3 outshines the bright central star of Orion, Betelgeuse, which measures around 0.5 in the scale. Its levels of visibility are comparable to notable stellar references such as Achernar in Eridanus and Procyon in Canis Minor, which score roughly 0.46 and 0.38 respectively.
Such intense artificial illumination in the night sky poses a challenge to astronomical research. The International Astronomical Union has proposed a brightness threshold near 7 for satellites to minimize contamination in observational data. If brightness levels exceed this threshold, imaging artifacts can be suppressed using artificial intelligence, while excessively bright objects may distort images beyond recoverable correction. BlueWalker 3 is estimated to be roughly 400 times brighter than the IAU’s recommended limit, and verification suggests that more facilities of this kind are planned, with AST SpaceMobile outlining ambitions to deploy around ninety additional units in orbit.
Speaking about the issue, a study co-author noted that the satellite launched with insufficient consideration for its impact on astronomy. The IAU has expressed a commitment to collaborate with the space industry to identify effective solutions that balance communication needs with the preservation of astronomical data. These insights emphasize the importance of early impact assessments and proactive mitigation strategies in future satellite design and deployment.
Experts have explored several approaches to mitigate the brightness challenge. One proposal involves relocating such satellites to a geostationary orbit, approximately 35,000 kilometers above Earth. In that position, the satellite would appear dimmer from the ground, reducing visual interference to roughly 99.98 percent of its current brightness. This transition would help protect sky visibility while still delivering the intended communication capabilities. The discussion reflects a broader trend toward orbital management that harmonizes space-based services with ground-based astronomical work.
Beyond the immediate brightness concerns, there is a wider cultural and scientific context. The phenomenon of light pollution has long dimmed the night sky for observers on the ground, diminishing the ability to study celestial bodies. The growing presence of bright satellites adds a modern dimension to this challenge, underscoring the need for coordinated policies that preserve the night sky for research, education, and wonder. In recent debates, the field has emphasized measurement, modeling, and transparency in sharing satellite brightness data so that astronomers can adapt observational strategies without compromising data quality. The conversation continues as new technologies emerge and as space-based networks expand across international boundaries, inviting ongoing collaboration between scientists, policymakers, and industry leaders. (Citation: International Astronomical Union; Nature journal)”