A study carried out from 50,000 observations in participatory sciences concludes that the invisibilization of stars increases at the rate of 10 % per year. If in a given place 250 stars are visible, only a hundred will be eighteen years later.
by Hugo Hayé
If in the light of the lampposts our streets are taking shape, the stars, they are fading. All the artificial lighting that illuminates our nights are the source of many consequences, especially environmental. We are talking about light pollution. A study published Friday, January 20 in the journal Science highlights the extent of its increase, underestimated until then.
The team of scientists led by Christopher Kyba, astrophysicist at the Research Center for German Earth Sciences, analyzed just over 50,000 observations with the nucleus of the night sky, collected from 2011 to 2022 by Citizens around the world as part of the Participatory Sciences Program The Globe At Night. One of their conclusions is the highlighting of a clear increase in light pollution in the past twelve years.
This was known, but so far the researchers monitored it using satellites measuring the light emitted by our installations from space. However, it turns out that the technical limitations of this method led to underestimate the extent of the phenomenon and the speed of its evolution. By relying on these observations made with the naked eye, Christopher Kyba thus calculated an invisibilization of the stars increasing by around 10 % per year, while the satellite measures estimated this pace to 2 %. According to Christopher Kyba, this figure means that, if in a given location, 250 stars are visible, eighteen years later, only one hundred will still be.
Passage to blue light
These results do not explain this magnitude of the growth of light pollution, too fast to come exclusively from the installation of new sources. Christopher Kyba hypothesizes that another factor participates in this phenomenon: the evolution of the nature of the lighting in the last decade. Indeed, the LEDs have appeared and began to replace incandescent bulbs and other types of lighting. However, they emit light with weaker wavelengths, also called “blue light”. Our eye is very sensitive to these wavelengths, then increasing the impact of this light on our vision of the night sky. In addition, this blue light diffuses more widely in the sky.
Sébastien Vauclair, astrophysicist specializing in the field of light pollution, however issues reservations concerning this study, in particular in terms of statistical reliability. Indeed, the data used come from a participatory science program, and the quantity of observations would be potentially insufficient to erase the approximations of measures and the weaknesses of the observation protocol.
You have 39.25% of this article to read. The continuation is reserved for subscribers.