Mercury,
March/April 2005 Table of Contents
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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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