The aftermath of supernovae… in Antarctica

It’s pretty amazing, all the things that get caught up in the Antarctic ice. It’s a prime hunting ground for meteorites, for one thing. The infamous ALH 84001 with its supposed martian microfossils was found in Antarctica. As was the tiny MM04, a rock which is probably older than planet Earth! But it’s not just rocks that get trapped in the Antarctic ice. Supernovae that lit up the night sky a thousand years ago have also left their marks.

Quite recently, a group of Japanese scientists spent some time in Antarctica looking for evidence of past supernovae. Specifically, supernovae which were seen in the years 1006 and 1054 (the latter of which caused the famous Crab Nebula). Both of these supernovae were recorded by astronomers at the time across the globe (particularly the Japanese, Chinese, European and Arabic astronomers). The team took ice core samples, and found large amounts of nitrogen oxides at times corresponding to 1006 and 1054. Curiously, there was another spike a while after 1054, the cause of which is still a mystery! If there was a third supernova that century, then for some reason no records of it exist.

A nearby supernova leaves its mark on Earth by drastically altering the atmosphere. A blast of gamma rays hitting the upper atmosphere will hit molecules of nitrogen and oxygen and rip them to shreds. Those fragmented molecules will then rapidly react, forming nitrogen oxides. The same thing happens in lightning bolts and even sunlight causes some nitrogen oxide to form, but only light from a supernova could cause such huge amounts all at once. This is the first time such evidence of past supernovae has been found in an ice core!

As well as the supernovae, the researchers got quite a haul of data — including finding increased levels of sulfate corresponding to volcanic eruptions across the globe, and a variation in background nitrogen oxide corresponding to the 11 year solar cycle.

It’s really quite amazing what gets recorded in the Antarctic ice!


(click to embiggen)

Sources: arXiv blog, arXiv

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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