Cooking Up Heavy Elements in the Cosmos

Mercury, March/April 2005 Table of Contents

Hubble Space Telescope image is courtesy of NASA, ESA, the Hubble Heritage Team (STScI/AURA), and H. E. Bond (STScI).

by Ignacio Birriel and Jennifer Birriel

The late Carl Sagan first introduced the public at large to the idea that "we are all made of star stuff." Since then, generations of introductory astronomy students have heard this mantra repeated.

Most people accept this "star stuff" statement at face value after having discussed the process of nuclear fusion in the cores of stars. Generally, only a few exceptionally inquisitive students venture beyond the simple statement to ask the question: "If massive stars can only fuse elements up to iron in their cores, then how do we get all the elements heavier than iron?"

We are "children of the stars"—made almost wholly of elements produced in stars. We know that all the hydrogen and most of the helium in the Universe was formed in the Big Bang. And that same creation event produced only traces of lithium. But all of the ninety-four naturally occurring elements heavier than hydrogen are produced by a variety of stellar processes. Furthermore, most of us are familiar with the thermonuclear fusion processes that take place in the cores of stars and generate the elements up to iron. Less familiar are the recipes for cooking up the elements above iron on the periodic table.

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