泥盆纪末期灭绝的超新星触发器
Supernova Triggers for End-Devonian Extinctions
摘要：
晚泥盆世是一个长期的低物种形成导致生物多样性下降，最终在泥盆纪-石炭纪边界附近的灭绝事件。最近的证据表明，最后的灭绝事件可能与平流层臭氧的急剧下降同时发生，这可能是由于全球气温上升。在这里，我们研究了另一种可能的原因，为假定的臭氧下降：附近的超新星爆炸，可能造成损害的加速宇宙射线，可以提供电离辐射高达$\sim 100$ kyr。因此，我们认为，泥盆纪末期的灭绝是由$\sim 20$ pc的超新星爆炸引发的，这在一定程度上超出了引发全面灭绝的“杀伤距离”。这种邻近的超新星很可能是由于大质量恒星的核心坍缩造成的;它们集中在太阳所在的薄银河系盘中。在一个或多个泥盆纪末期灭绝地层中检测到长寿命放射性同位素Sm-146或Pu-244，将证实超新星起源，指向大质量恒星的核心坍缩爆炸，并探测超新星核合成。超新星假说的其他可能的测试进行了讨论。
英文摘要：
The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian-Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to $\sim 100$ kyr. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at $\sim 20$ pc, somewhat beyond the "kill distance" that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core-collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes Sm-146 or Pu-244 in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosythesis. Other possible tests of the supernova hypothesis are discussed.
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