Star Stuff

A CarlSagan phrase from his television series Cosmos. The elements heavier than lithium are only formed by nuclear fusion deep within stars. When a star is large enough, it ends its life by exploding, scattering these elements into the vacuum.

Eventually the resulting nebulae condense into stars again. Our solar system evolved from such debris. Our sun is at least second generation. Most of our world was forged in the heart of a long dead star. Each of us is made of StarStuff.

AndyPierce clarifies: Both hydrogen and helium are thought to have been synthesized in abundance in the big-bang along with trace amounts of lithium. Nevertheless essentially all elements other than hydrogen and helium are thought to arise from nuclear processes within stars. In astronomy, all elements other than hydrogen and helium are called "metals". Nuclear fusion is only energetically favorable for elements up to iron. Some of the energy of supernovae explosions goes into energy-consuming fusion reactions to create elements heavier than iron, in addition to distributing the stellar matter throughout the cosmos. You can get an idea of which 'generation' a star is by spectral analysis to determine the star's 'metallicity'.

CarlSagan also said, "If you want to bake an apple pie from scratch, you must first create the universe." Damn. That baklava's going to take longer than I thought.