Shaoni Bhattacharya looks at what is – and isn’t – being done to help ensure everyone can see the stars
The stars have always been part of human culture. From motifs on Greek pottery to van Gogh’s Starry Night painting, the connection is evident across the globe. But today, there are few people who get to experience what our forebears saw every night in the sky, researcher Christopher Kyba tells me.
“If you went outside at night you would have had the whole cosmos staring down at you – this really difficult to understand thing,” says Kyba. “From my experience with stars, it makes you quite reflective. It changes how you think – this confrontation with awe.”
The light pollution from humanity’s use of lights at night is reducing the number of stars we can see. Year on year it worsens, threatening our connection with the night sky, not to mention the implications for astronomy, wildlife, health, the climate and energy wastage.
To the human eye, the night sky is brightening by about 10 per cent a year, according to a recent study in Science by Kyba, a physicist at Ruhr University Bochum, Germany, and his colleagues. At this rate, a child born in a location where 250 stars are visible at night would only be able to view 100 by the time they reach adulthood at 18. “That’s a really fast and dramatic change,” says Kyba.
He and his colleagues attribute this decrease in star visibility to ‘skyglow’ – an artificial twilight caused by streetlights, LED signs and residential lighting, scattering off molecules in the atmosphere. While most of this light escapes into space, some of it bounces back down towards Earth.
Measuring the dark
Their research draws on data collected by the ongoing Globe at Night project run by the US National Science Foundation’s NOIRLab based in Tuscon, Arizona, which amassed over 51,000 observations made by citizen scientists around the world between 2011 and 2022. Volunteers compared their naked-eye view of the sky at night to a set of star maps, to find what was the faintest star visible. This helped gauge the skyglow, as the brighter the background becomes, the more that faint stars are rendered invisible to the unaided eye.
“What we found is that the charts that people are choosing are rapidly shifting towards the charts that have fewer stars,” says Kyba.
In fact, the data showed the fall in the number of stars visible was equivalent to an avera
