M51是一个著名的漩涡星系，位于猎犬座。1773年梅西叶发现了它，但当时以为它是一片星云。M51旁边还有一个小一些的星系，它的编号为：NGC5195。
M51, whose name comes from being the 51st entry in Charles Messier's catalog, is considered to be one of the classic examples of a spiral galaxy. At a distance of about 30 million light years from Earth, it is also one of the brightest spirals in the night sky. A composite image of M51, also known as the Whirlpool Galaxy, shows the majesty of its structure in a dramatic new way through several of NASA's orbiting observatories. X-ray data from NASA's Chandra X-ray Observatory reveals point-like sources (purple) that are black holes and neutron stars in binary star systems. Chandra also detects a diffuse glow of hot gas that permeates the space between the stars. Optical data from the Hubble Space Telescope (green) and infrared emission from the Spitzer Space Telescope (red) both highlight long lanes in the spiral arms that consist of stars and gas laced with dust. A view of M51 with the GALEX telescope shows hot, young stars that produce lots of ultraviolet energy (blue).
M51它被认为是旋涡星系最经典的范例之一。它距离地球3000万光年，也是夜空中最明亮的旋涡星系之一。NASA的轨道天文台合成照片用一种戏剧性的新方式展现了M51（又名涡状星系）的宏伟结构。来自NASA钱德拉X射线天文台的X射线数据揭示出的是点状源（紫色），这是双星系统中的黑洞或中子星。钱德拉还探测到了弥漫在在星际空间的热气体辐射。来自哈勃太空望远镜的可见光数据（绿色）以及斯必泽太空望远镜探测到的红外辐射（红色）凸显了旋臂上的恒星长带与点缀着尘埃的气体。来自GALEX望远镜的M51图象展示的则是年轻的热星，它们产生了大量的紫外辐射（蓝色）。
The textbook spiral structure is thought be the result of an interaction M51 is experiencing with its close galactic neighbor, NGC 5195, which is seen just above. Some simulations suggest M51's sharp spiral shape was partially caused when NGC 5195 passed through its main disk about 500 million years ago. This gravitational tug of war may also have triggered an increased level of star formation in M51. The companion galaxy's pull would be inducing extra starbirth by compressing gas, jump-starting the process by which stars form.
人们认为，教科书式的旋臂结构是M51与邻近的星系邻居NGC 5195（图中上方）正在进行相互作用的结果。一些模拟工作表明，M51明晰的旋臂结构部分成因是5亿年前NGC 5195穿过了星系的主盘。引力拔河赛触发并促进了M51中的恒星形成活动。伴星系的拉力会以压缩气体的方式引发额外的产星活动，气体的压缩正是恒星形成过程的开端。
来源:NASAhttp://www.nasa.gov/multimedia/imagegallery/iotd.html
http://chandra.harvard.edu/photo/2007/m51/
[ 本帖最后由 寻找拉玛 于 2008-2-14 13:21 编辑 ] |
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