Free Astronomy Magazine March-April 2026

E xtensive urban skyglow shows how arti- ficial light from a metropolitan region creates a bright dome above the horizon, significantly reducing night-sky darkness over large areas. [A. Anfuso] 500-900 nm range; it was thus ex- tremely effective at monitoring the traditional yellow-orange part of the spectrum emitted by high-pressure sodium (HPS) lamps, which domi- nated outdoor lighting worldwide. Unfortunately, the emission spec- trum of white LEDs is particularly strong in the blue region, peaking at around 450-460 nm, meaning it falls almost entirely out- side the VIIRS detection range. In a 2014 study by C. Cao & B. Bai, it is estimated that approxi- mately 34% of the radi- ant power of typical white LED lighting falls outside VIIRS’s response, and as the use of LED technology ramps up worldwide, this number is likely set to rise. Fortunately, this gap is now being filled with fresh data coming from the SDGSAT-1 (Sustain- able Development Sci- ence Satellite 1), the first A dense urban skyline with artificial light- ing significantly increases sky brightness and pre- vents the visibility of stars. [A. Anfuso] satellite specifically designed for the UN’s 2030 Agenda for Sustainable Development. Launched by the Chi- nese Academy of Sciences in 2021, it provides Earth observation data with thermal infrared, low-light, and multispectral sensors to moni- tor human-nature interactions, ur- ban development, and environmen- tal changes. Comparative studies between VIIRS and SDGSAT-1 show a significant and systematic underestimation of global light pollution, particularly around urban centres. Where VIIRS data suggested stable or even de- clining trends, SDGSAT-1 revealed a rapid increase in blue-rich emissions, signalling a significant miscalcula- tion in our previous estimations.