[11] Muller's breakthrough was to find a way to date" how long ago any particle was melted——meaning he could build up a picture of whether the moon gets a constant barrage¹ or suffers spells of intense bombardment.

　　[12] He said; "The evidence clearly shows that the moon has gone through spells of relatively² frequent impacts and others of reduced intensity³. I believe it is likely that this is because the Oort Cloud is being disturbed by a massive body that is throwing comets out of stable orbits, a small fraction of which could reach the Earth."

　　[13] Muller and others believe that the dark star probably takes about 26m years to complete an orbit around the sun.

　　[14] Other scientists have already noted⁴ that mass extinctions of life on Earth seem to occur in a pattern with gaps equivalent to multiples of 26m, suggesting some regular event is causing the comets to come Earth's way.

　　[15] The best-known such event was the one that wiped out the dinosaurs⁵ 65m years ago, but that was not the worst; the planet has suffered several such large mass extinctions

　　[16] Astronomers⁶ have found the first Earth-sized planet orbiting another star. The discovery raises the chances of finding planets that could support life as we know it.

　　[11]马勒的突破是他找到了一种确定粒子被融化的年代的方法，这意味着他可以确立这样一幅画面，即月球是受到接二连三的轰击还是经历了间歇性的强烈的粒子辐射。

　　[12]他说："有迹象清楚表明，月球经历了比较频繁的撞击，以及其它强度减少的撞击。我认为这可能是由于奥尔特云受到一个正在把彗星抛出稳定轨道的大天体的扰动，其中一小部分彗星可能会到达地球。"

　　[13]马勒和其他一些人认为，这颗暗星绕太阳运行一周大约要用2600万年的时间。

　　[14]另一些科学家已经注意到，地球生物的物种灭绝现象出现的间隔是2600万的倍数，这说明了某个规律性事件造成彗星降临在地球上。

　　[15]这类事件中最著名的一个就是6500万年前恐龙的灭绝，但这还不是最坏的；这个星球已经经历了几次如此大规模的灭绝。

　　[16]天文学家已经发现了第一个像地球一样大小的围绕另一颗星运行的行星。这个发现增加了找到我们熟知的能维持生命的行星的机会。