图片来源:http://chandra.harvard.edu/photo/2008/catseye/
http://www.nasa.gov/multimedia/imagegallery/iotd.html
译文来源:每日天文一图 (北京天文馆镜像)http://www.bjp.org.cn/apod/2008-08/04/content_8671.htm
This composite of data from NASA's Chandra X-ray Observatory and Hubble Space Telescope is a new look for NGC 6543, better known as the Cat's Eye nebula. This famous object is a so-called planetary nebula that represents a phase of stellar evolution that the Sun should experience several billion years from now. When a star like the Sun begins to run out of fuel, it becomes what is known as a red giant. In this phase, a star sheds some of its outer layers, eventually leaving behind a hot core that collapses to form a dense white dwarf star. A fast wind emanating from the hot core rams into the ejected atmosphere, pushes it outward, and creates the graceful filamentary structures seen with optical telescopes.
Chandra's X-ray data (colored in blue) of NGC 6543 shows that its central star is surrounded by a cloud of multi-million-degree gas. By comparing where the X-rays lie in relation to the structures seen in optical light by Hubble (red and purple), astronomers were able to deduce that the chemical abundances in the region of hot gas were like those in the wind from the central star and different from the outer cooler material. In the case of the Cat's Eye, material shed by the star is flying away at a speed of about 4 million miles per hour. The star itself is expected to collapse to become a white dwarf star in a few million years.
X射线下拍摄到的猫眼星系
影像提供：Ｘ-射线NASA/CXC/SAO; 光学: NASA/STScI
说明：行星状星云NGC6543内绚丽的图案已经说明了它那广为人知的名字：猫眼星云。从1995年，哈勃太空望远镜就开始拍摄绚丽的假色光学影像，详细地揭示了这个炽热星云内的旋涡状结构，该星云被认为是一颗类似太阳的垂死恒星吹出了外层气体罩之后形成，它距离我们地球3,000光年远。这张合成影像合成了猫眼星云最新的哈勃光学影像以及钱德拉天文台拍摄的最新X-射线数据，揭示了其内令人吃惊的致密X-放射线，这就表明星云内存在着极度炽热的气体。X-放射线以蓝色调，层次不一地出现在星云的中央。很明显，星云的中央星处于数百万度的高温中，Ｘ射线放射出气体。而另一部分Ｘ-射线放射出的炽热气体遇上了在光学波段下的强烈较冷气体，很明显可以看到，扩张的气体正雕蚀着可见猫眼星云内的灯丝状物质和结构。凝视着猫眼星云，天文学家们看到了我们太阳的命运，在大约50亿年之后最终将进入行星状星云阶段。
[ 本帖最后由 寻找拉玛 于 2008-8-5 21:48 编辑 ] |
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