Everything has a beginning, and our story begins when the cloud that was the Solar Nebula began to contract. All stars exist in islands called galaxies, and galaxies contain old and new stars as well as clumps of dust clouds. These clouds contain mostly hydrogen and some heavier metals (any elements that are heavier than helium is considered a metal by Astronomers). As we will learn the the Sun section, stars create their energy by a process called fusion. When a star ends its life, it explodes in a tremendous phenomenon called a supernova. A supernova has so much energy that heavy metals are formed - metals like iron and gold. These elements "seed" surrounding hydrogen clouds so that newer stars will contain more heavy elements in their atmospheres.
It is believed that for a system of planets to form around a star during cloud contraction the cloud must contain heavy elements.
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