Why do elements with atomic # beyond iron exist?

[RexDart]

My albeit simplified understanding of the universe:

At one point in time there was nothing but hydrogen in the whole universe, which coalesced into stars. Through a process of fusion, the hydrogen was used up as star-fuel, then the resulting helium was fused and so on until it gets to iron (#32?), at which point it can no longer fuse so the star explodes and sends metal elements all over the place which end up forming new stars and planets and so forth.

Anyways, it was my understanding that this process always stops at Iron, that stars never go beyond that element in their fusion process. So I can see how we have all the elements up to Iron, but how do we have naturally occuring elements with higher atomic numbers than Iron, like Gold or Silver for instance?

[DreadCthulhu]

When stars go supernova, there exist enough heat an pressure, for a brief period of time, to form heavier elements.

[robby]

From here:

[In stars], lighter elements fuse and form heavier elements. These reactions continue until the nuclei reach iron (around mass sixty), the nucleus with the most binding energy. When a nucleus reaches mass sixty, no more fusion occurs in a star because it is energetically unfavorable to produce higher masses. Once a star has converted a large fraction of its core’s mass to iron, it has almost reached the end of its life.

…Some stars keep shrinking until they become a cooling ember made up of iron. However, if a star is sufficiently massive, a tremendous, violent, brilliant explosion can happen. A star will suddenly expand and produce, in a very short time, more energy then our Sun will produce in a lifetime. When this happens, we say that a star has become a supernova.

While a star is in the supernova phase, many important reactions occur. The nuclei are accelerated to much higher velocities then can occur in a fusing star. With the added energy caused by their speed, nuclei can fuse and produce elements higher in mass than iron. The extra energy in the explosion is necessary to overcome the energy barrier of a higher mass element. Elements such as lead, gold, and silver found on Earth were once the debris of a supernova explosion. The element iron that we find all through the Earth and in its center is directly derived from both super novae and dead stars.

[RexDart]

Ahhhh, so the supernova process itself manages to fuse elements past iron, there was my mistake in understanding. Mega-thanks, sirs.

Truly the universe is awesome.

[Diletante]

Also, it is an oversimplification to say that stellar fusion process stops at iron. Normal stellar fusion can create elements heavier than iron, but the process absorbs more energy than is released, unlike fusion of lighter elements. So the fusing of iron does not further the chain reaction like the fusing of hydrogen or helium.

[MC_Master_of_Ceremonies]

I’d just like to point out that hydrogen wasn’t the only element nucleosyntheised before the first stars, others are deuterium (an istope of hydrogen), helium and lithium as well as small quantites of other elements such as boron.