Monday, December 7, 2009

We are made of star stuff

I'm currently reading the very cool book Death From The Skies!, by Phil Plait, which outlines a bunch of end-of-the-world scenarios and then talks about the science behind them. Phil's an astronomer, and a fantastic writer - I've been a fan of his ever since I was about 15 years old, when I discovered his hilarious Bad Astronomy website (his review of the movie Armageddon still makes me chuckle).

Death From The Skies! is one of those books where you just end up thinking "wow, science is so darn cool!". Being a bit of a geek for pretty much my entire life, I thought I knew a reasonable amount about astronomy and astrophysics, for someone who's a non-specialist. But every chapter of Death From The Skies is full of things that I haven't encountered before - and many of these tidbits are extremely cool.

One particular chapter on supernovae is full of "wow-facts". In this chapter, Phil talks about the processes of fusion in the core of massive stars. Our own sun fuses hydrogen nuclei to produce helium, but more massive stars can produce other elements by fusion, once their hydrogen supply has run out. Massive stars produce, in this order, carbon, neon, oxygen and silicon; and the most massive stars in our universe have such tremendous pressure and heat at their core that they can produce iron. These stars, however, do not have long to live once they are producing iron, and will soon explode in a furious cascade of events that we call a supernova.

The early universe contained only three elements: hydrogen, helium, and a little bit of lithium. Nothing else. Then supermassive stars started to form, and began creating heavier elements from the lighter ones, right up to iron, then exploded. The explosions of these stars triggered the formation of new stars... and the cycle continued.

I'll leave you with (what I think is) the most striking paragraph of this chapter:

When you cut your finger and a thin rivulet of blood seeps up into the slice, the red color you see is due to hemoglobin, and the key factor in that molecule is iron. That iron was forged in the heart of a supernova.

As Carl Sagan told us: We're made of star stuff.

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