112 — Terrestrial effects of moderately nearby supernovae

Melott & Thomas (10.1101/230847)

Read on 10 December 2017
#supernova  #paleontology  #atmosphere  #evolution 

This is an extremely badass name for a paper.

Every century, this paper estimates that there are about three supernovae in our galaxy. In order to be viewed on Earth without specialized equipment, the events must be relatvely close (within only a few hundred light years). This paper focuses on supernova events that took place during the late Miocene and another near the Pliocene-Pleistocene boundary, 8 and 3 million years ago, respectively.

The paper explains that since supernovae generally result from the deaths of large stars, and large stars generally remain close to their siblings due to their short lifespans, it is likely that planets such as Earth would experience these events rarely for long stretches of time, and then in “bursts” for short periods of time.

The results of these events may be very unnoticeable on Earth — but if the conditions are right, certain types of supernovae, called Type IIP, would give off very bright visible light. At 150 light years away from Earth, this sort of event would be brighter than the light from the moon, and would come from a small point in the sky, making it visible even during the day. Such bright blue light might have strange effects on plant life and even animal circadian rhythm. (The paper notes that this phase would only last for about two weeks, though, so it’s unlikely we’d see fossil evidence.)

The constant bombardment of cosmic rays from these dying stars could likely influence the ozone layer, depleting ozone as the rays interact with the oxygen molecules. This could create up to a 50% UVB-light increase on the surface of Earth, damaging DNA and other biological compounds. Further, the higher rate of ionization of the atmosphere would increase the rate of lightning, potentially causing more wildfires.

This sort of paper is super fun to read because such a seemingly irrelevant event — such as supernova explosions in our galaxy millions of yers ago — could have made large changes to the evolutionary fate of earthling species. With any luck, we won’t have to find out any time soon if these predictions were accurate.