影像版權與提供: Rick Krejci (RicksAstro Astrophotography)
While searching the skies above 18th century France for comets, astronomer Charles Messier diligently recorded this object as number 27 on his list of things which are definitely not comets. So what is it? Well, 20th century astronomers would classify it as a Planetary Nebula ... but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is now known to be an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is about 1,200 light-years away in the constellation Vulpecula. This intriguing color composite view was recorded through narrow band filters sensitive to emission from hydrogen atoms (shown in red) and oxygen atoms (shown in blue/green).
在18世紀法國的夜空中搜索彗星時，天文學家梅西葉勤奮地在他的一張肯定不是彗星的天體名單上，記錄了這個編號為27的天體。 既不是彗星，那麼它會是什麼呢？在21世紀，天文學家會將它分類為行星狀星雲，但是實際上它也不是行星，只是用小型的望遠鏡觀測時，它具有行星的圓盤狀外觀而已。 如今，天文學家已經知道梅西葉27(M27)是一個非常典型的發射星雲，它是類似太陽的恆星在耗盡核燃料後所產生的。 當恆星的外層被拋到太空中時，外層物質的原子受這顆即將死亡恆星發出的強烈紫外光激發，因此發射出可見光形成所謂的行星狀星雲。 又稱為啞鈴星雲的這團對稱雲氣，位在狐狸座內，離我們約有1千2百光年遠。這張有趣的組合彩色影像，是透過窄波段濾鏡所拍攝的；來自氫原子的輻射著色成紅色，氧原子的輻射則為藍色和綠色。
資料來源: Scientific American
Department of Physics, NCKU