2021年06月30日

Simulation: Formation of the First Stars
Video Credit:
Harley Katz (U. Oxford) et al.

Explanation: How did the first stars form? To help find out, the SPHINX computer simulation of star formation in the very early universe was created, some results of which are shown in the featured video. Time since the Big Bang is shown in millions of years on the upper left. Even 100 million years after the Big Bang, matter was spread too uniformly across the cosmos for stars to be born. Besides background radiation, the universe was dark. Soon, slight matter clumps rich in hydrogen gas begin to coalesce into the first stars. In the time-lapse video, purple denotes gas, white denotes light, and gold shows radiation so energetic that it ionizes hydrogen, breaking it up into charged electrons and protons. The gold-colored regions also track the most massive stars that die with powerful supernovas. The inset circle highlights a central region that is becoming a galaxy. The simulation continues until the universe was about 550 million years old. To assess the accuracy of the SPHINX simulations and the assumptions that went into them, the results are not only being compared to current deep observations, but will also be compared with more direct observations of the early universe planned with NASA’s pending James Webb Space Telescope.

Tomorrow’s picture: open space


模拟:第一代恒星的形成
影片提供:
Harley Katz (U. Oxford) et al.

说明: 第一代恒星是如何形成的?为找出答案提供助力,特地进行斯芬克斯电脑模拟,看在极早期的宇宙恒星如何形成,而部分的成果可参见这部主题影片。在画面的左上角,可见到从爆炸起算以百万年为单位的时间。很明显的,纵然在大爆炸1亿年之后,宇宙各处的物质仍然过于均匀,以至于恒星无法形成。此时宇宙里除了背景辐射之外,仍然非常幽暗。不过,接下来很快的,密度稍高富含气的物质结,开始聚集成第一代的恒星。在这部缩时影片里,紫色为气体,白色是光,金色则是能够电离氢,并把它分解成电子和质子的高能辐射。金色区块也标示出,以强烈超新星爆炸谢幕的最大质量恒星。而嵌在画面里的白圈,则突显即将形成星系的区域。这项模拟一直进行到宇宙年龄约5亿5千万年方止。为了评估斯芬克斯模拟及模拟奠基的假设之正确性,模拟的成果不但会和目前的深空观测进行比对,未来也会与美国航空航天局即将发射的詹姆斯韦伯太空望远镜,对早期宇宙的较直接观测比对。 (SPHINX simulations 斯芬克斯模拟;SPHINX为传说里的带翼狮身女怪,据说会拦路要行人猜谜,猜不出者即被噬食。)

明日的图片: open space

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