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Accretion of Galaxies and Stars
Transcript of Accretion of Galaxies and Stars
Outline how the accretion of galaxies and stars occurred through:
expansion and cooling of the universe
subsequent loss of particle kinetic energy
gravitational attraction between particles
lumpiness of the gas cloud that allowed gravitational collapse to occur
What is Accretion?
Accretion refers to the gradual accumulation of matter in one place.
Expansion and Cooling
The expansion of the Universe results in a corresponding drop in temperature, as the energy has to be distributed throughout a larger volume of space. According to the Big Bang theory, the universe, originally in an extremely hot and dense state that expanded rapidly, has since cooled by expanding to the present state, and continues to expand today.
Subsequent loss of particle Kinetic Energy
Heat energy is a result of the kinetic energy of particles. As space expanded the temperature decreased as the particles lost kinetic energy.
Further loss of kinetic energy means that the force of gravity between atoms is greater than the force which is causing expansion.
This allows atoms to bond into molecules and molecules to accrue together, gradually gaining more gravitational force until they begin to fuse into heavier elements in the first primitive stars present in small clusters called protogalaxies.
Gravitational attraction between particles
Lumpiness of the gas cloud that allows gravitational collapse
After the "Big Bang" there was an uneven distribution of the hydrogen and helium gas cloud allowed gravitational attractiveness force to act collecting gas particles together into larger masses.