All the gold in the world

Gold, element 79 named Au

The element 79, gold is a precious metal unalterable very popular since the dawn of time. Pure gold is a noble metal, the most malleable and ductile metal known, it is both dense and soft.
The amount of gold extracted by man is estimated in late 2008 to 163 kilotons, a small cube of about twenty meters.
In 2010, gold reserves were estimated at 51 kilotons. China stands in the foreground with 13.8% of world production in 2010, followed by Australia with 10.2%, United States, 9.2%, Russia 7.6%, Africa South, 7.6% and Peru 6.8%.
Where does the gold of the earth?
Gold is produced in stars like all the elements of matter found on Earth. Stars are nuclear reactors whose fuel will change during its life cycle. When the runaway nuclear reaction, the heart of the star contracts it, the temperature rises and the nuclear reactions restart with a new fuel.
Thus the life of a star is a series of gravitational contraction and nuclear fuel cycles.
Hydrogen is the most abundant element in the known universe, in fact, it represents 75% of the total mass and 92% of all the atoms of matter. This is the main constituent of stars, gaseous planets, nebulae and interstellar gas.
Every second, stars convert millions of tons of hydrogen (H) into energy through nuclear fusion that combines hydrogen nuclei to form helium nuclei (He).
The star then burns slowly, so efficient and it takes billions of years.
Helium is the second constituent of the universe.
When they burned all their hydrogen reserves, stars collapse, increasing internal temperature, and continue their combustion by converting helium into carbon (C), at this stage it is called 'flash of 'Helium'.
Then, the carbon is transformed into nitrogen (N), nitrogen, into oxygen (O). The oxygen into silicon (Si).
The evidence produced in a combustion cycle are used as fuel in the next cycle.
As to the combustion cycles are becoming shorter as the fuel becomes less and less energy.
These are the most massive stars that are making all chemical elements up to number 26, that ie, iron (Fe).
Then they will grow, exhaust the gas in their nuclei and the upper layers are cool.
This sequence will cause an explosion in the upper layers, and their projection in interstellar space. Thus we find in the nebulae, the first elements up to iron.

And gold?
Appear to see the gold, it will take a cataclysmic cosmic event, a massive explosion, that of a supernova.
A supernova appears as a new star to the Earth, hence the name, nova.
But in fact the explosion of the massive star, leads to total destruction. It was during the supernova explosion the star releases the chemical elements, which it summarized in its life and during the explosion itself. This cosmic event occurs only for stars much larger than our Sun, from 1.5 to 5 times its mass.
The violent death throes of the star causes an explosive collapse terrible. Its radius shrinks to 10 km, the final density is enormous, the nuclei of elements can not resist and heart explodes, throwing the upper layers of the star into space. It will appear as well as other heavier elements beyond element 26 (iron), such as cobalt, nickel, copper, zinc, gallium,...
And gold?
Above 5 times the mass of the Sun, the collapse of the star is even more violent. The nuclear reaction can not be stopped.
The heart of the star becomes a black hole.
As in the previous case a gigantic explosion, will project the upper layers of the star in space, hundreds of billions of miles, seeding the interstellar medium even heavier elements such as platinum, gold, mercury, lead, uranium, plutonium...
These heavy elements are distributed in very small quantities, in the nebulae of gas and dust.
Other cosmic events cause the creation of heavy elements like gold, especially the collision or merging of two neutron stars.
All of these will be found in the solar system and therefore in the planets. It is in the core of the Earth has the highest gold, billions of tons, but gold is scarce in the crust, still we find "a lot" and is well distributed on the surface of the Earth.
The distribution of gold on Earth would be 0.004 mg of gold per cubic meter of material.
Studies show that the concentration of gold in the Earth's crust is between one hundred and a thousand times too high compared to the original nebula.
A simulation conducted in 2011 has helped to explain the abundance of gold on the surface.
The gold found on the surface of the Earth, come from the late great bombardment, which took place there are 3.8 billion years, at a time when billions of meteorites bombarded Earth.

Image: Gold is produced in the supernova, like all heavy chemical elements found on Earth. Above, the image of the gold mask of Tutankhamun, pharaoh of the 18th Dynasty (14 century BC. JC).

NB: The shock wave from the supernova favors the formation of new stars, accelerating the contraction of regions of gas and dust in the interstellar medium.
The novae, unlike supernovae come from thermonuclear explosions, causing a partial destruction of the star by expelling part of its surface into interstellar space. Our sun will not end its life as a supernova but much quieter, as a yellow dwarf.