2021年04月26日:人马三重星云-（A Sagittarius Triplet）--原图下载
Image Credit &Copyright:Gabriel Rodrigues Santos
说明: 用望远镜巡礼人马座和恒星群集的银河中心之时，这三个明亮星云经常是目光会聚的天体。其实远在十八世纪时，梅西叶就编录了其中的两个星云，它们分别是影像中右下方的大星云M8和顶缘附近的美丽M20。第三个发射星云是M8左方的NGC 6559，二者由一道黝黑尘埃带所分隔。这三个星云，都是距离在5千光年左右的恒星诞生区。跨幅超过100光年的庞大M8，亦名为礁湖星云，而M20常见的暱称是三叶星云。影像中，明亮氢气云发出的红光，是这些发射星云最主宰性的色泽，而三叶星云内高对比的泛蓝区域，则来自被尘埃所反射的星光。这片宽广的星际视野，横跨约4度（8个满月宽度）的天区。
原文：
Image Credit &Copyright:Gabriel Rodrigues Santos
Explanation: These three bright nebulae are often featured on telescopic tours of theconstellation Sagittarius and the crowded starfields ofthe central Milky Way.In fact, 18th century cosmic touristCharles Messiercataloged two of them; M8,the large nebula below and right of center,and colorful M20near the top of the frame.The third emission region includesNGC 6559, left of M8 andseparated from the larger nebula by a dark dust lane.All three are stellar nurseries aboutfive thousand light-years or so distant.Over a hundred light-years across the expansive M8is also known as the Lagoon Nebula.M20's popular moniker is the Trifid.Glowing hydrogen gas creates the dominant red color of theemission nebulae.But for striking contrast, blue hues in theTrifid are due to dust reflected starlight.Thebroad interstellarscapespans almost 4 degrees or 8 full moons on the sky.
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