Classification of dark night environment level standards of National Astronomical Observatories, Chinese Academy of Sciences (NAOC), has been released

Since the Industrial Revolution, the pursuit of lighting for humanity has gradually evolved into an out-of-control disaster of light pollution. Artificial light at night (ALAN) scatters the constituents of the atmosphere (such as gas molecules, aerosols, and clouds), causing the artificial glow to brighten the night sky during observations.1 The unrestrained expansion of urban lighting systems and the unrestrained flashing of commercial neon lights have led to an annual increase of 6% in the brightness of the night sky. Around the city, people can no longer see the Milky Way with the naked eye. This kind of light pollution not only obscures the starry sky but also disrupts the circadian rhythm that has formed in the ecosystem of Earth over millions of years; every year, millions of birds lose their way due to the strong light in cities and crash into tall buildings. The foraging and breeding behaviors of nocturnal animals have been severely disrupted, and biodiversity continues to decline. Human health itself is also threatened. Excessive night light can inhibit the secretion of melatonin and increase the risk of cancer and cardiovascular diseases.

Due to light pollution, astronomers are gradually losing sight more observable celestial bodies. In addition, the large-scale launch of satellites (megaconstellations; e.g., 12,000 Starlink Internet satellites)2 will also have a serious impact on ground-based astronomical observations, and the total global artificial light increase in the past decades was 2% per year on average.3 The larger the observation field of view and the longer the exposure time, the greater the impact will be. Each satellite leaves a very obvious trajectory within the observation field of view, polluting the observation data, and it is difficult to completely eliminate it through data processing. This influence is not only on optics but also has a significant impact on observations in the radio wave band.

In 2022, Qinghai Province promulgated the provision “Regulations on the Protection of the Astronomical Observation Environment in Lenghu, Haixi Mongolian and Tibetan Autonomous Prefecture.” The content includes the following. The Lenghu astronomical observation environment area is divided into the dark night protection core area and the dark night protection buffer area. The core area refers to the area within 50 km outward from the geometric closed area boundary of the overall development plan site selection of the Lenghu astronomical observatory, and the buffer area is 50 km outward from the boundary of the core area. In the core area for dark night protection, the types and brightness of light sources must be strictly controlled. The illumination direction of all outdoor fixed night lighting facilities should be 30° below the horizontal line. In the core area of astronomical observation environment dark night protection, no projects that may affect the local astronomical observation environment are allowed to be planned or constructed, no activities that may affect the astronomical observation environment are permitted, and so on. This regulation came into effect on January 1, 2023, and it was the first local regulation in China for the protection of dark night skies. Meanwhile, for the city of Shenzhen, on August 31, 2021, the “Shenzhen Urban Lighting Specialized Plan (2021–2035)” has been issued, which established the “dark night protection zone” for the first time in China. Later in 2023, Shenzhen issued the “Light Environment Standards for Dark Communities,” systematically stipulating the brightness of the night sky, air glow, indirect scattering of sunlight, starlight scattering, and the background brightness of the night sky caused by artificial light. Then, in March 2023, the Xichong District was certified as an International Dark Night Community by the International Dark-Sky Association (IDA), making it the first one in China. It is believed that more and more professional astronomical observatories will be protected by local governments, such as those in Lenghu and Pingtang. Dark Night Communities, such as that in Xichong, will spring up everywhere.