藍色的礁湖星雲
Blue Lagoon <br />
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<img src="http://i16.tinypic.com/2ez2ukp.jpg" border="0" onclick="zoom(this)" onload="attachimg(this, 'load')" alt="" /><br />
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影像版權與提供: Russell Croman <br />
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<font color="navy">Explanation: </font><br />
Stars come and go as you slide your cursor over this engaging image of M8, aka the Lagoon Nebula. Of course, the nebula is itself a star-forming region, but the stars that appear and disappear here include background and foreground stars that by chance lie along the same line of sight. In this "for fun" comparison of two nearly identical digital images, the stellar point sources were removed from one image by computer processing to leave only the diffuse emission from the glowing gas clouds. In both pictures, red emission (H-alpha emission) from atomic hydrogen dominates the cosmic lagoon's visible light, but narrow band filters were used to record the image data and map the hydrogen emission to green hues, with emission from sulfur atoms in red and oxygen in blue. The lovely Lagoon Nebula spans about 30 light-years at an estimated distance of 5,000 light-years toward the constellation Sagittarius. <br />
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<font color="navy">說明: </font><br />
隨著鼠標滑過及離開上面這張迷人的M8 (礁湖星雲)影像，恆星會出現或隱沒。雖然礁湖星雲是個恆星誕生區，但影像或顯或隱的前景及背景恆星，只是恰巧在這幅影像的視線方向而已。為了"好玩"而製做的這二幅幾乎相同之數位影像，點狀的星點是經過電腦處理加以去除，只留下會發出瀰漫輝光的雲氣。在這二張照片裡，來自原子氫的紅色輝光 (H-alpha輻射)，在可見光礁湖星雲影像裡，它們是最主要的輻射，但在透過窄波段濾鏡所拍攝的上面影像裡，氫輻射特地以綠色來上色，而來自硫和氧原子的輻射，則分別用紅色和藍色來著色。美麗的礁湖星雲位在人馬座內，距離我們約有五千光年遠，跨度約為30光年。<br />
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<font size="2">資料來源: Scientific American<br />
Department of Physics, NCKU</font>