ESSE 1010 Lecture Notes - Protostar, Solar System
3 Nov 2011
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Document Summary
A cloud of interstellar gas/dust, the solar nebula , including material formed in previous generations of stars, is disturbed (for example, by the shock wave from a nearby supernova): contraction: the cloud starts collapsing under its own gravity. Within the core of the sun: temperature exceed 15,000,000 c, pressure is 340 billion times the atmospheric pressure at earth"s surface, conditions are so intense that nuclear fusion takes place creating new elements. Four hydrogen nuclei get fused into one helium nucleus, accompanied by the emission of neutrinos and release of energy: H1 is the nucleus of a hydrogen atom (one proton) He4 is the nucleus of a helium atom (two protons and two neutrons) The nucleus of the resulting helium atom is about 0. 7 percent less massive than the four component protons. During the fusion of hydrogen approx 0. 7% of the mass of hydrogen is converted into energy. Fast-moving ions can escape the sun"s gravitational attraction.
