More than 11,000 years ago, a massive, supergiant star came to the end of its life. The star’s core collapsed to form an incredibly dense ball of neutrons, and its exterior was blasted away in an immense release of energy astronomers call a supernova.

The light from this supernova first reached Earth from the direction of the constellation Cassiopeia around 1667 A.D. If anyone alive at the time saw it, they left no records. It is likely that large amounts of dust between the dying star and Earth dimmed the brightness of the explosion to the point that it was barely, if at all, visible to the unaided eye.

The remnant of this supernova was discovered in 1947 from its powerful radio emission. Listed as Cassiopeia A, it is one of the brightest radio sources in the whole sky. More recently, the Wide-field Infrared Survey Explorer (WISE), detected infrared echoes of the flash of light rippling outwards from the supernova.

In the image, the central bright cloud of dust is the blast wave moving through interstellar space heating up dust as it goes. The blast wave travels fast – at about 6% the speed of light. By the time WISE took this image, the blast wave has expanded out to about a distance of 21 light-years from the original explosion. The flash of light from the explosion, traveling at the speed of light, has covered well over 300 light-years. The orange-colored echoes further out from the central remnant are from interstellar dust that was heated by the supernova flash centuries after the original explosion.

The false colors in this image represent different wavelengths of infrared light, which is invisible to the human eye.

Image Credit: NASA/JPL-Caltech/UCLA


11000多年前,一颗巨超巨星走到了生命尽头恒星的核心坍塌,形成了一个密度极高的中子球,它的外部被炸开,释放出巨大的能量,天文学家称之为超新星

大约在公元1667年,这颗超新星发出的光第一次从仙后座方向到达地球。如果当时还活着的人看到它,他们就没有留下任何记录。垂死的恒星与地球之间的大量尘埃可能会使爆炸的亮度变暗,以至于肉眼几乎看不到爆炸(如果有的话)。

这个超新星的残余是在1947年从其强大的无线电发射发现的。被列为仙后座A,它是整个天空中最亮的无线电源之一。最近,广域红外巡天探测器(WISE)探测到了超新星发出的涟漪状闪光的红外回声。

在图片中,中央明亮的尘埃团是穿过星际空间的爆炸波,它使尘埃升温。冲击波传播速度非常快,约为光速的6%。在WISE拍摄这张照片的时候,爆炸波已经扩展到距离原始爆炸大约21光年的距离。爆炸产生的光以光速传播,覆盖了300光年。在离中央遗迹更远的地方,橙色的回声来自星际尘埃,这些尘埃在最初的爆炸几个世纪后被超新星闪光加热。

该图像中的假色代表了人眼不可见的红外光的不同波长。

图片来源:NASA/JPL-Caltech/UCLA

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