Nature reports Earth hit by large cosmic ray event AD 774

[gary]

An article published on 3 June 2012 in Nature reports on a finding that two
ancient cedar trees that were analyzed by researchers from Nagoya University in
Japan show a surge in carbon 14 dating to AD 774 ~ 775.

The source of the carbon 14 is likely to be from cosmic rays that had collided
with the stratosphere and reacted with nitrogen before being absorbed into
the biosphere.

Abstract of Nature article here -
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11123.html

The authors of the paper argue that neither a solar flare nor a supernova is likely to have
been responsible.

They suggest that it is unlikely to have been as a result of a solar flare because
it would have had to been far bigger than any known flare.

There is also no known historical record of a supernova at that time.

In an article in the Sydney Morning Herald on the finding, it is reported that
both the Cassiopeia A and Vela Junior supernova remnants appear to be too
far away to be the smoking gun either.

So the mystery deepens.

Sydney Morning Herald story here -
http://www.smh.com.au/technology/sci-tech/mystery-8thcentury-cosmic-blast-captured-in-trees-20120604-1zr8k.html

[OICURMT]

How big are these cedar trees at 1200 yrs old?

[Blue Skies]

Very interesting! Thanks for the heads up on that one, gary.



Probably not that big, but the wood is very hard and dense due to their slow growth, which makes them great for doing dendrochronology on.

[Paul Haese]

Those are only babies. There are trees in the united states that are nearly 4800 years old. See here (http://en.wikipedia.org/wiki/List_of_oldest_trees)

[jenchris]

There's an Arctic Beech in Tamborine that is over 2000 years old

[AstralTraveller]

It's amazing that we can find such things. Something happened in 'outer space' over 1300 years ago and we can 'see' it through a relatively minor change in a tiny trace constituent of a tree. [The deviation is 12 permil but the error bars for individual determinations are 4-5 permil.] Science is amazing, even if doing it can be difficult, tedious and even boring.



You need that and a highly seasonal climate to give nice regular, countable rings. Eucalypts can produce nice dense wood but dendrochronology is Aust is difficult in the south and impossible in the north.

[Blue Skies]

That's a good point. It wouldn't be much use trying to do anything past 500 years in WA as the weather doesn't change much from season to season. I'm usually forced to roll my eyes every time some passionate protester claims the trees are "thousands of years old" here. Not! They're just surprisingly fast growers for their size. Still impressive and worth saving, though, I wont argue with that, just wish they'd get the facts right... hmm, on reflection there probably are some plants here might age in the 1000's put they're not trees. Macrozamias and Xanthorrhoea's come to mind.

[OICURMT]

Cooooooool... thanks for the link

Makes me wish I were an "Ent".