Caption: First place in the 2021 IAU OAE Astrophotography Contest, category Light pollution. Light pollution results from the excess of artificial light produced by human endeavours mainly as a side effect of industrialisation. This kind of pollution is usually most noticeable around well populated areas associated with intense human activities, such as street lighting, lights from the transportation system, buildings and houses. But it can also come from other places, such as ships and oil platforms in the sea. This image taken in a national park in Belgium in 2018 shows the detrimental effect of light pollution on the most precious resource that connects all humans together – the night sky.
Credit: Dong Han/IAU OAE

Caption: 2021 年國際天文學聯合會 OAE 天文攝影比賽光汙染類第二名。 這張2020年在斯洛伐克拍攝的合成圖展示了光汙染地區因人工照明造成的影響。光汙染越嚴重，我們能觀測到的天空景象就越少。注意從右到左，即使對於靈敏的數碼相機，能看到的星星數量也在減少。光汙染不僅影響夜空中天體的可見度，還對生態系統產生重大影響，許多動物也受到了負面影響，例如遷徙的夜行鳥可能會遇到難以找到遷徙方向的問題，海龜可能會被海灘附近沿海城市的燈光所迷惑，從而錯過產卵的地點。光汙染還可能對人類健康產生負面影響。因此，保護黑暗寧靜的夜空對整個地球及其上豐富的生命至關重要。
Credit: Tomáš Slovinský/IAU OAE

Caption: Third place in the 2021 IAU OAE Astrophotography Contest, category Light pollution. This image of Venus and the Pleiades also shows the tracks of the Starlink satellites. These satellites which are located at an altitude of approximately 550 kilometres, are part of an ever-growing constellation of satellites aimed to provide worldwide internet access. The reflective surfaces of the satellites, coupled with the fact that they are orbiting around the Earth, means that astronomical observations which require very long exposures capture “tracks” of the satellites in their images. Astronomical images used for scientific research are not usable because the measurements and data will contain these “tracks”. Because the number of satellites is expected to grow, it is likely that in the near future there will be no place on Earth where these satellites will not be visible crossing the sky. This is a new type of light pollution that seems to be an upcoming problem we will have to deal with, as these satellites might prevent optimal observation of the sky.
Credit: Torsten Hansen/IAU OAE