our sun forms

Supernova explosions distribute all the common elements such as Oxygen, Carbon, Nitrogen, Calcium and Iron into interstellar space where they enrich clouds of Hydrogen and Helium that are about to form new stars. They also create the heavier elements (such as gold, silver, lead, and uranium) and distribute these as well.

The formation of the sun, although not altogether clear, was basically the result of fragmentation and gravitational collapse of an interstellar cloud of gas and dust. This may well have caused nearby supernova explosions leading to the formation of a primordial solar nebula. The sun then formed in the densest, central region. It is so hot there that even silicates, which are relatively dense, had difficulty forming. The sun formed within a cloud of gas in a spiral arm of the Milky Way Galaxy.

During its first 50 million years, the sun contracted to approximately its present size, where gravitational energy released by the collapsing gas heated the interior, and when the core was hot enough, the contraction ceased and the nuclear burning of hydrogen into helium began in the core. A vast disk of gas and debris that swirled around this new star then gave birth to planets, moons, and asteroids. In our planetary system, we live on the third-closest planet to the sun. The phenomena of being so hot close to the sun (silicates) may account for the presence near the sun of a planet such as Mercury having a relatively small silicate envelope and a larger than usual dense iron core. It is easier for iron dust and vapour than for lighter silicates to coalesce near the central region of a solar nebula. At larger distances from the centre of the solar nebula, gases condensed into such solids are found today from Jupiter outwards.

- Tt, ASh (ed)