Tuesday, August 26, 2014

More on the possible AD 774/775 hit on the Earth by a nearby GRB

I hadn't heard of either the odd AD 774/775 values of the C12/C14 and increased B10 ratios or the hypothesized casue: a nearby (within the Milky Way) Gamma Ray Burst before reading a blog post by Greg Laden related to climate change a while ago.

It turns out the GRB hypothesis was only recently advanced: Hambaryan & Neuhäuser, 2013, MNRAS, 430, 32 [full article text available online here]. Back at the time Phil Plait actually covered the story in his blog, which has a nice write up of the idea and why other explanations (Solar Flare, Magnetar, nearby Supernova) are claimed to be less likely than a "short" (neutron-star merger induced) GRB.

It somewhat surprises me that an event of the magnitude necessary to alter the isotopic composition of the Earth's atmosphere in less than a few seconds could occur without (a) anyone seeing anything and recording it, and more over (b) not causing any significant biological events (e.g. animal, plant or human deaths). Still, reality often runs counter to naive expectation (i.e. "common sense") so I'm not too put off the idea by that.

For now I'd view this idea of the Earth getting hit by a short GRB as a plausible hypothesis rather than concrete fact, at least until several more studies come to the same conclusion. Still, it is a rather fun and exciting idea.

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