Thursday, November 30, 2006

Did a starburst in the Milky Way 2.4 billion years ago have affect life on Earth?

2.4 billion years ago a storm of Cosmic Rays produced by an increase in the star formation rate of our home galaxy (the Milky Way) ionized the Earth's atmosphere to such an extent it changed the climate, triggering spurts of growth and die-backs in the primitive life on the Earth at that time.

That is the sure-to-be-highly-controversial suggestion in a new paper by Danish scientists (H. Svensmark, 2006, Astronomische Nachrichten, 27, 871) reported on by space.com. When I get back from the honeymoon I'll have to check out the full paper and write a more detailed follow up of this.

As a starburst guy I've love for this to be true, but right now it is best to be skeptical. That Cosmic Rays (CR) strongly affect the Earth climate appears to be by no means well established, and has often been used by climate-change deniers (e.g. see this older post of mine about CR-driven climate change claims made by [strangely enough!] the exact same Danish group).

Also there are issues about the significance, duration, and effect any upturn in Galactic star formation at that time may have been - even if there were a major burst in the MW its by no means clear how the CR flux at Earth would have been altered.

I'll look into these and other issues later...

[update 14/12/06 (1) I still haven't got around to reading the paper in full. (2) Typo in title has been corrected]

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