A new research study that looked at and compared light pollution levels at major astronomical observatories around the world found that light is polluting the sky above most observatories and that immediate action will be needed to decrease the amount of pollution from artificial light sources.
The study, published in the Monthly Notices of the Royal Astronomical Society, contains light pollution levels from nearly 50 observatories around the world, ranging from small amateur observatories to the largest professional observatories. The researchers used a model of light propagation in our planet’s atmosphere and applied it to nighttime satellite data.
According to the Royal Astronomical Society, light pollution is traditionally measured by examining the brightness directly overhead. The researchers used additional indicators such as the average brightness at an angle of 30 degrees above the horizon, the average brightness at the first 10 degrees above the horizon, the overall average brightness across the sky, and the brightness of the floor of the artificial light. coming from the night sky.
For the study, these indicators were compared to the natural brightness of the sky caused by airglow and light from stars in the Milky Way. This comparison revealed that light pollution at major observatory sites is much higher than previously assumed.
The researchers found that only seven of the study’s 28 primary observatory sites (observatories with a telescope that has a diameter of three meters or more) have zenith (directly overhead) sky brightness with light pollution below. of the one percent threshold. This means that the other 21 observatories are all above the level and therefore face light pollution.
Ground telescopes usually have the lowest pointing direction of about 30 degrees above the horizon. Only one of the 28 observatories had light pollution below the 1% level in this part of the sky. In fact, two thirds of the main observatories have exceeded the higher threshold of 10%.
According to the researchers, this light pollution threatens the future of ground-based telescopes and should be addressed immediately to ensure the observatories can continue to produce important astronomical work.