  Isotope analyses on meteorites, planets, lunar samples, the solar wind, and
solar flares show that heterogeneous debris of a supernova (SN) that exploded
here 5 Gy ago formed the solar system. The Sun formed on the collapsed SN core.
Iron meteorites and the iron cores of the terrestrial planets formed out of
iron-rich material surrounding the SN core. Giant gaseous planets formed out of
the light-weight elements in the outer SN layers. Mass separation enriches
light elements like H and He at the solar surface, but the bulk Sun consists
almost entirely of the same seven, even-numbered elements that comprise 99% of
ordinary meteorites - iron (Fe), oxygen (O), nickel (Ni), silicon (Si),
magnesium (Mg), sulfur (S) and calcium (Ca).
