You are reading a tafsir for the group of verses 81:2 to 81:3

وَإِذَا النُّجُومُ انكَدَرَ‌تْ (and when the stars will swoop down...81:2). The word inkadarat is derived from inkidar and it denotes 'to fall'. The righteous predecessors have interpreted it thus. It signifies that all the stars from the sky will fall into the oceans as explained in the preceding verses.