Cassiopeia A

The above image was made by the Spitzer Space Telescope. Images were made through filters 3.6-micron light (blue); 4.5-micron light (green); and 8.0-micron light (red). Exposures were made on 20 November 2003 & 2 December 2004

上述图像由斯皮策太空望远镜制作。通过3.6微米光（蓝色）、4.5微米光（绿色）和8.0微米光（红色）的滤光器进行成像。曝光时间分别于2003年11月2日和2004年12月2日进行。

Cassiopeia A is a supernova remnant at distance 11,000 light-years in our galaxy in the consellation Cassiopeia. The original star, about 15 to 20 times more massive than our sun, died in a cataclysmic "supernova" explosion relatively recently in our own Milky Way galaxy. Using the additional information from the infrared capability of Spitzer, researchers could piece together the details of the explosion, layer by layer. "Now we can better reconstruct how the star exploded," said Dr. William Reach of NASA's Spitzer Science Center, Pasadena, Calif. "It seems that most of the star's original layers flew outward in successive order, but at different average speeds depending on where they started."

Cassiopeia A 是一个距离我们银河系约 11,000 光年的超新星遗迹，位于天琴座。这颗原始恒星的质量大约是太阳的 15 到 20 倍，曾在相对较近的过去在我们自己的银河系中发生了一场剧烈的‘超新星’爆炸。利用斯皮策望远镜的红外能力，研究人员能够逐层拼凑出爆炸的细节。‘现在我们可以更好地重建这颗恒星是如何爆炸的，’来自美国国家航空航天局斯皮策科学中心的威廉·雷奇博士说，‘似乎这颗恒星的原始各层是按顺序向外飞出的，但不同层次的平均速度取决于它们起始的位置。’

Cassiopeia A provided excellent data for studying the anatomy of a supernova explosion. Because it is young and relatively close to our solar system, it can be observed carefully with many instruments. In a few hundred years or so, Cas A's scattered remains will have completely mixed together, forever erasing important clues about how the star lived and died.

Cassiopeia A提供了研究超新星爆发解剖结构的优质数据。由于它年轻且相对接近我们的太阳系，可以使用多种仪器仔细观测。在几百年内，Cas A的残骸将完全混合在一起，永远抹去关于这颗恒星生与死的重要线索。

It is thought that the associated supernova may have occurred near 1680 when a star near that location was recorded by , but later could not be found. Cassiopeia A is the strongest radio source in the sky outside the solar sytem. The supernova remnant was found among the earliest discrete radio sources, in 1947 by radio astronomers from Cambridge, England. This radio source was first named Cassiopeia A and later cataloged 3C 461. Its optical counterpart coudn't be found until a more precise position was obtained, by radio interferometry in 1950. Consequently, David Dewhirst of Cambridge obtained first deep optical photos of this region in the sky and discovered a strange faint nebula, which was then investigated by Walter Baade and Rudolph Minkowski with the then-new Palomar 5-meter telescope (Baade & Minkowski, 1954). Spectroscopic observations soon confirmed its nature as the rapidly expanding shell of a supernova remnant, also cataloged as G111.7-2.1. Within two years, American astronomers were able to determine its angular expansion rate, and calculated back that the expansion must have started around the year AD 1667.

人们认为，与之相关的超新星可能发生在1680年左右，当时该地区附近有一颗星被记录下来，但后来无法找到。Cassiopeia A是太阳系外天空中最强的无线电源。1947年，英国剑桥的无线电天文学家发现了这个无线电源，它是最早被识别出的离散无线电源之一。该无线电源最初被命名为Cassiopeia A，后来被归类为3C 461。直到1950年通过无线电干涉测量获得更精确的位置，才找到了其光学对应物。因此，剑桥的David Dewhirst获得了该区域的首次深光学照片，并发现了一个奇怪的微弱星云，随后由Walter Baade和Rudolph Minkowski使用当时新建成的帕洛马5米望远镜进行了研究（Baade & Minkowski, 1954）。光谱观测很快确认了其性质，即为一个迅速扩展的超新星遗迹壳层，也被称为G111.7-2.1。两年内，美国天文学家能够确定其角扩张速率，并计算出扩张必须始于公元1667年左右。