Free Astronomy Magazine March-April 2026

7 MARCH-APRIL 2026 ASTRO PUBLISHING still cheaper, generating savings that are frequently reinvested to illumi- nate areas that were previously left dark, such as parks, architectural fa- cades, and suburban corridors. The shift toward blue-rich lighting is particularly damaging to astron- omy, as shorter wavelengths scatter far more efficiently than longer ones; it is estimated that blue light around 440 nm scatters about 2.5 times more than the green-yellow light (550 nm). This means that a single white LED contributes disproportionately more to the diffuse dome of skyglow, even if its total lumen output is lower than that of the lamp it re- placed. And the phenomenon is not limited to urban centres: scattered light can travel long distances, de- grading the sky far beyond the city and reaching remote areas once considered safe. The growing impact of artificial skyglow has therefore not gone unnoticed within the as- tronomical community as even ma- jor ground-based observatories, such as the Vera C. Rubin on Cerro Pa- chón and the Very Large Telescope on Cerro Paranal, both in Chile, are now affected by light pollution, with severe consequences for their effi- ciency and scientific output. Large telescopes operate close to physical and technical limits, and wide-field imaging programmes and time- domain surveys rely on stable, dark sky backgrounds for the detection of faint and diffuse signals. As sky brightness increases, the impact on scientific output is inevitable, partic- ularly for studies targeting low-sur- face-brightness phenomena. L arge-scale skyglow generated by artificial lighting and enhanced by atmospheric scattering over an urbanised area. [A. Anfuso] Blue light, the dominant driver of modern light pollution, was largely absent from the datasets that guide global assessment and policy discus- sions: the night sky changed faster than we could detect with our in- struments, and it’s now a significant problem. These new satellite data depict a clear and uncomfortable picture: total artificial radiance is constant- ly rising globally, even in regions where data suggest a decrease in energy consumption for lighting. The rapid rise in light pollution is driven by the increasing efficiency of LEDs in a paradox known as the “rebound effect”: light has become cheap — so we use more of it. Also, as is often the case, new instal- lations are significantly brighter than the lamps they replace, although