Astronomy Picture of the Day——夜空：暗夜降临
Dark Skies: Turn on the Night
Image Credit & Copyright: Jeff Dai
Explanation: Have you ever experienced areally dark night sky? One common and amazing feature is the glowing band ofour Milky Way galaxy stretching from horizon to horizon. If you live in or neara big city, though, you might not know this because city lights reflecting offthe Earth's atmosphere could only allow you to see the Moon and a few stars.Today, however, being UNESCO's International Day of Light, the InternationalAstronomical Union is asking people to Turn on the Night by trying to betterunderstand, and in the future better reduce, light pollution. You can practiceeven now by going to the main APOD website at NASA and hovering your cursorover the Before image. The After picture that comes up is a panorama of fourexposures taken with the same camera and from the same location, showing whathappened recently in China when people in Kaihua County decided to turn downmany of their lights. Visible in the Before picture are the stars Sirius (leftof center) and Betelgeuse, while visible in the After picture are thousands ofstars with the arching band of our Milky Way Galaxy. Humanity has lived formillennia under a dark night sky, and connecting to it has importance for bothnatural and cultural heritage.
夜空：暗夜降临
你是否经历过真正的暗夜呢？一个共同且令人惊叹的特征是横跨天空的银河系发光带。如果你住在大城市，你可能就不知道这一点，因为地球大气反射了城市灯光，这使你只能看到月球和数颗恒星。然而，今天是联合国教科文组织设定的国际光日，国际天文联合会要求人们通过更深入的理解和在未来更好地减少光污染来开启暗夜。现在，你可以通过访问NASA的APOD网站来实现，这两幅全景影像是用同一架相机从同一地点拍摄的四张曝光照片结合而成，它呈现了中国最近发生的事情，当时开化县的人们决定关掉大部分灯光。在前一幅影像中可以看到天狼星（位于中央左侧）和参宿四，而在后一幅影像中可以看到我们银河系的拱形光带和数千颗恒星。人类已经在黑暗夜空下生活了数千年，与之相关的事物对自然和文化遗产来说都具有重要的意义。
参考资料：
https://apod.nasa.gov/apod/image/1905/TotnBefore_Dai_1080.jpg
https://apod.nasa.gov/apod/image/1905/TotnAfter_Dai_3000.jpg
近期文章：
Astronomy Picture of the Day——哈勃望远镜拍摄的苍白旋涡星系NGC 4921