The supernova left behind a dense central core 12.5 miles wide that was first spotted in 1999 by NASA's Chandra X-ray Observatory.

超新星爆发后留下了一个直径12.5英里的致密核心，NASA的钱德拉X射线天文台于1999年第一次观察到了这一核心。

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A small, dense object only twelve miles in diameter is responsible for this beautiful X-ray nebula that spans 150 light years.

一个小的，只有十二英里的直径重的对象是这个美丽的X射线星云负责横跨150光年。

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Sperm sorting can be carried out either by putting live sperm in a dense liquid and spinning it in a centrifuge to separate sperm carrying the x chromosome and those carrying the y chromosome.

BBC: Q&A: Sex selection

The aim of the trial was to see if it made the women's breasts easier to examine in mammograms because young women's breast tissue is dense, making it hard for X-rays to pick up tumours.

BBC: Hormone spray 'could stop cancer'

Traditional X-ray film too often does not detect small, early cancers, especially in breasts with dense tissue.

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