仙后座A

2021年01月23日

Recycling Cassiopeia A
Image Credit: X-ray – NASA, CXC, SAO; Optical – NASA,STScI

Explanation: Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After a few million years, the enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the stellar life cycle. Light from the explosion which created this supernova remnant would have been first seen in planet Earth’s sky about 350 years ago, although it took that light about 11,000 years to reach us. This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help astronomers explore the recycling of our galaxy’s star stuff. Still expanding, the outer blast wave is seen in blue hues. The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core.

Tomorrow’s picture: massive galaxy

仙后座A
影像提供: X-ray – NASA, CXC, SAO; Optical – NASA,STScI

说明: 我们银河系内的大质量恒星，过着绚烂亮丽的日子。它们从庞大的宇宙云气塌缩诞生出来，当核心的核子火炉点燃之后，就不停在核心合成重元素。经过数百万年后，恒星发生垂死爆炸，把制造出的物质炸回星际空间，让恒星形成重新开始。上面影像中这个称为仙后座A的超新星遗迹，就是恒星生命循环最后阶段的例证之一。虽然在350多年前，人类在地球的夜空中，看到产生这个遗迹的超新星爆炸，不过爆炸的亮闪经过约11,000年才传到地球。这张假色影像，整合钱德拉X射线卫星的X射线与哈伯太空望远镜的可见光数据，以突显遗迹里依然炽热的云气丝和物质结。依仙后座A的估计距离来换算，它的宽度约为30光年。影像中，元素发出的高能X射线辐射，以不同的色泽来标示：矽为红、硫为黄、钙为绿及铁为紫，让天文学家得以探索我们银河系的造星物质，如何回收与再利用。而仍然在扩张的震波前缘，则以蓝色来呈现。影像中央附近的亮斑是一颗中子星，是崩塌大质量恒星核孑遗的极端致密天体。

明日的图片: 大质量星系