科學圖說

M27啞鈴星雲(M27 Dumbbell Nebula)

M27啞鈴星雲是行星狀星雲，紅色光主要來自氫的發射譜線（H alpha），藍綠色的光，來自雙電離氧離子的發射譜線（OIII）。
其中OIII這條譜線是發生機率非常低的能階跳躍譜線，難以在地球上實驗室找到，只能在宇宙裡稀薄廣大的星際空間發現。
此圖以寬帶濾鏡拍攝，曝光20分鐘再加以合成，達到小望遠鏡數十小時累積曝光該有的效果。

M27 Dumbell Nebula is a planetary nebula. The red light is produced by the emission spectrum of hydrogen (H alpha). The bluish green light is produced by the emission spectrum of doubly ionized oxygen (O III). The O III spectrum has a very low probability of energy level transition, making it very difficult to replicate in a laboratory on Earth but can be found in diffuse and planetary nebulae. This image was obtained using a broadband filter. Exposure time was set at 20 min to achieve what would have required dozens of hours of accumulated exposure using a small telescope.