Supernovae blasts shape climate, life on Earth, reckons boffin
'Our world's biology is reflection of the sky'
A new paper by cosmic ray researcher Henrik Svensmark suggests that the abundance of diversity of biological life on Earth is closely correlated to our planet's proximity to supernovae.
Svensmark, a professor of physics at the Center for Sun-Climate Research at the Danish Space Research Institute, revealed his work in a paper published by the Royal Astronomical Society.
The prof reconstructed the relative rate at which stars within 850 parsecs of our solar system went supernova over the past 510 million years, and compared it to geophysical and paleobiological records.
He concluded, poetically, that: “...remarkable connections to the long-term histories of life and the carbon cycle have shown up unbidden. Biodiversity, CO2 and the carbon-13 (δ13C) isotope (a proxy for photosynthesis) all appear so highly sensitive to supernovae in our galactic neighbourhood that the biosphere seems to contain a reflection of the sky.”
When our solar system passes through one of the galaxy’s rotating arms, it is brought closer to exploding supernovae, which increases the quantity of cosmic rays reaching Earth’s atmosphere. The intense bombardment from a supernova may last around 1,000 years.
Svensmark suggests climate, rather than mutation, accounts for the correlation. He posits that the Permo-Triassic Extinction Event, which saw the mass death of almost all sea life on Earth, was not caused by a comet or asteroid, but rather by a fall in cosmic ray bombardment. Where cosmic ray exposure spiked, there was a corresponding sudden and short-lived falls in sea level and brief glaciations, he asserted.
Earlier work by astronomer Brian Fields had suggested Earth was within a supernova’s “kill radius” – 30 light years – a dozen times over 4.5 billion years.
You can download the paper here [PDF, 2.8MB], read the society's announcement here, and find a lucid layman’s explanation here, written by former BBC science editor Nigel Calder who also co-authored the book The Chilling Stars (2007) with Svensmark. ®
The galaxy's arms are density waves, and all the stars in the galactic disk periodically pass through them. The most everyday example of a density wave is when you are driving along a busy motorway and the traffic abruptly slows to a crawl or stand-still for no apparent reason. Viewed from space at night, it is actually possible to see waves of traffic density moving in the opposite direction to the traffic. Another example is density waves of Guiness moving through the head as it settles.
Re: Supernovae effecting our planet ...
Well, yes, it's quite possible that the shockwave from a supernova several billion years ago compressed a cloud of gas and dust in just the right way that it went on to form the solar system, and therefore Earth. A supernova is certainly responsible for the formation of that dust.
Oh, you meant to say "affect"? Carry on then.
in the "layman's version" link...
"A mark of a good hypothesis is that it looks better and better as time passes. With the triumph of plate tectonics, diehard opponents were left redfaced and blustering. In 1960 you’d not get a job in an American geology department if you believed in continental drift, but by 1970 you’d not get the job if you didn’t. That’s what a paradigm shift means in practice and it will happen sometime soon with cosmic rays in climate physics.
Plate tectonics was never much of a political issue, except in the Communist bloc. There, the immobility of continents was doctrinally imposed by the Soviet Academy of Sciences. An analagous diehard doctrine in climate physics went global two decades ago, when the Intergovernmental Panel on Climate Change was conceived to insist that natural causes of climate change are minor compared with human impacts.
Don’t fret about the diehards. The glory of empirical science is this: no matter how many years, decades, or sometimes centuries it may take, in the end the story will come out right."
...mine's the one with the April snow on it, thanks.